Let's go back over the events with some speculation about Thrall's motivation, and connecting of dots. Thrall, despite his pride in being an orc and orc traditions and spiritualism, is not a typical orc by any stretch of the imagination. Taken in by humans when he was still an infant, Thrall's first memory of an encounter with an orc wasn't until he was twelve years of age. He was raised by a family who, while wary of him, had a daughter that treated him like he was a brother -- like he was just another human -- and then taught to read and write, taught the ways of combat, of honor, of mercy. He didn't even see the outside world until he was eighteen, at which point he escaped his imprisonment and fled.
An orc with no idea what his people were, no idea how to speak orcish, no idea what it meant to be an orc, was then captured and shuttled into an internment camp with the rest of his 'kind'. Note the quotes. What happens next? Thrall sees people just like him, captured and enslaved just like he had been -- but for some strange reason, curiously lacking the desire to escape that he possessed. What was wrong with these people? He was told of an orc that had eluded the humans and their imprisonment, Grom Hellscream -- an orc who lived with the same lethargy of the orcs in the camps, but instead of submitting to it, fought it each and every day.
So he sought out Grom Hellscream, and convinced him that it wasn't good enough that Hellscream fought the lethargy alone -- that the orcs needed to be freed, to be shown that there was a better life out there. But why exactly did Thrall do this? What was the motivation for an orc raised by humans to do something for a group of individuals he knew little to nothing about? Thrall was taught to read, yes -- but the books he was presented were human history, not orc history. The humans knew very little of orcs, as demonstrated by Blackmoore's lack of understanding that any baby, even an orc baby, needs milk to survive.
Was Thrall really seeking the redemption of his people, or was he merely trying to find his place in the world, and fill it with people as he saw fit? The point could be argued endlessly, but everything Thrall did from that point forward stirred something in the hearts of the orcs locked away in the internment camps. They saw in Thrall the possibility of survival, and they saw in the shaman Thrall had become a demonstration of power that had not been seen since the First and Second Wars. The orc race was a fairly primitive one back on Draenor -- shamanistic in their beliefs; and orc society was very much based on dominance. The strongest orcs were the orcs in power; the weaker orcs were the ones that followed. Warchiefs led, peons did the grunt work. It was the way of life. In Thrall, they saw a potential leader, and with every display of power, culminating in the destruction of Durnholde at the hands of the shaman, the orcs faith in him grew.
Nobody argued when Doomhammer made Thrall second in command -- Thrall was the only orc showing any kind of initiative at the time. He sought out Hellscream, he sought out the Frostwolf, and that drew the attention of Doomhammer. Nobody argued when Thrall was made Warchief, either. It can be argued that the very characteristics that make Thrall so human, the compassion, the wisdom, the intelligence, were what drove the orcs to rally behind the new Warchief. Barely twenty, twenty-one when the Horde moved to Kalimdor. Incredibly young, for an orc -- but the rest of the Horde followed him, because he led the way, and because the alternative was going back to enslavement or possible execution at the hands of the Alliance.
Over the course of the next seven years, the blind devotion that the orcs of the internment camps demonstrated slowly began to wane. Their Warchief has done what, to the eyes of an orc, is inconceivable -- suggested that they ally with the very people that he freed them from. What sense is there, in the eyes of an orc that has seen countless battles with the Alliance, seen hundreds upon hundreds of their fellow warriors slain by the humans, spent years imprisoned by those very same humans, in turning around and allying with the very people that had been their enemy for so long?
This is where Thrall made his first mistake -- in assuming that his people were not so very different from the humans that had enslaved them. He assumed that his fellow green-skinned orcs were so savage and brutal, that Grom Hellscream was so ruthless and bloodthirsty solely because of the demonic taint that had haunted them all since the blood pact with Mannoroth had been enacted. He continued trying to demonstrate to his people that there was a better way, all the while seeking a way to show them that the orcs didn't used to be like this. And so he sought out the orcs of Draenor, now Outland, in an effort to find the orcs that hadn't been corrupted, that remained pure to the old spiritual ways of his people.
This is where Thrall made his second mistake -- in assuming that the ancient orcs of Draenor were peaceful, spiritual people with little interest in needless bloodshed. What Thrall didn't, and couldn't know was that his people were initially the primitive sort that while peaceful, followed the ways of brute strength and shows of dominance to establish superiority. He couldn't know this because humans raised him -- he had no idea what the original orc race was like.
Enter Garrosh Hellscream, the uncorrupted son of Thrall's best friend, mentor, and brother of the heart. Garrosh, to Thrall, was everything that Grom could have been had he not taken that first drink of Mannoroth's blood. Brown-skinned and the leader of a somewhat gentle group of native orcs, Garrosh was older than Thrall, but at the same time younger in so many ways -- as he'd lived the entirety of his life in Nagrand and was largely unaware of Azeroth's existence, or the existence of Thrall and the new Horde. Garrosh was convinced he was doomed to repeat the failures of his father, a father that had abandoned him in Nagrand and never returned, and a father that had carelessly damned their entire race to servitude.
This is where Thrall made his third, and worst mistake of all -- he told Garrosh that his father was a hero, but that wasn't the crux of his error. He saw in Garrosh the potential of an uncorrupted Grom, and brought him back to Azeroth. That was the worst possible thing he could've done. To Thrall, Garrosh would be an example to his people -- an orc uncorrupted by the fel taint that had plagued the orc race for so long, an orc with the strength of his father, but lacking the savage bloodthirst that the Blood of Mannoroth had granted his father. Garrosh was suddenly a stranger in a strange land, surrounded by the green-skinned descendants that his father had freed. His father, the hero. His father, the leader. And Garrosh was faced with the daunting task of living up to his father's heroic reputation, something that he leapt upon with zest.
As for Thrall... yes, Thrall was responsible for filling Garrosh in on his father's destiny, but Thrall was also... strange. He insisted on trying to ally with enemies, something that made as little sense to Garrosh as it did to the orcs of the internment camps. Thrall advertised caution rather than charging into battle with honor, a strange idea to an orc. To a true orc, to an orc brought up on Draenor, to an orc with orcish ideals and years of orcish behavior to back him up. Thrall was younger than Garrosh, and yet he led the entirety of the Horde, not with brute strength and dominance, but with odd speeches of diplomacy.
Not only that, but Thrall refused to place Garrosh in any kind of leadership role. Garrosh was designated as an advisor, nothing more -- and Garrosh's bloodline, the bloodline of Hellscream yearned for more. Grom was not bent on power because of the Blood Pact; he took the Blood Pact because he desired power. Garrosh is very much his father's son, and bent on obtaining power wherever he can get it.
The orcs of the internment camps, the original orcs that Thrall led to freedom, are left with two potential leaders that they are looking at: Thrall, a young orc raised by humans with odd, foreign ideas of peace and diplomacy that seem almost suspiciously human... or Garrosh, brought from Draenor and representing everything the orc race could have been had they not taken that pact with Mannoroth. Garrosh, an orc that knew that the best way to show another orc you were stronger was to beat them over the head until they gave in. Garrosh, an orc that doesn't tout silly ideals about allying with old enemies, but speaks instead of war, brutality, savagery, the very things that make an orc's heart sing.
This is where the player base comes in. The Horde players of World of Warcraft, and the players of Warcraft III were introduced to Thrall as the idea of the 'noble savage'. Thrall was introduced as a character that players could relate to, a way to make the Horde less 'evil' and more sympathetic in the eyes of the people playing the game. While you can simply play through Warcraft III as a complete game and watch the story of Thrall and the Horde from beginning to end, with World of Warcraft, the story is evolving around those very players -- and they have a much more intimate influence and connection with the characters in WoW than they ever did with WC3. The idea and concept of Thrall was a wild success, and embraced so thoroughly that players tend to forget where the orcs originally came from, and what they are at heart.
Garrosh is absolutely despised because of this. He represents everything that Thrall was introduced for in an effort to reform player's opinions of the orcs. No sympathy, no mercy, and no redeemable qualities, what Garrosh represents is simply this: an orc. What Thrall represents is this: a human-like orc, pretending to be a real orc and force the rest of orc society to pretend, right along with him.
The orcs of the Horde are walking a very, very thin line, one that narrows with each passing day. While players protest that Thrall is a good Warchief, and Garrosh a terrible choice as a potential new leader, what they fail to realize is that yes, Thrall is a good person with good ideals, but these are not the sort of ideals an orc usually carries. Garrosh on the other hand represents everything that an orc should be, to an orc. Do I believe that Garrosh would be a good Warchief? From the standpoint of a player, a human being, oh heck no he'd be about the worst choice possible. But this is, again, from the standpoint of a player and a human being -- not the standpoint of an orc.
What the orcs face in upcoming months and in the new expansion is utter and complete civil war, with the players stuck in the middle to watch the events as they unfold. Whether Thrall admits defeat at the hands of Garrosh, or beats Hellscream's hide and settles back into his mission of peace is still unknown -- but the orcs are not going to have an easy time in Cataclysm, and they aren't the only ones affected by civil unrest. Take a look at the current political situation for the blood elves, forsaken, tauren and trolls for some further insight.