EA DICE has been a fairly prolific developer during the current console generation, churning out both a high-profile title based on original IP (Mirror's Edge), as well as ones based on established franchises like Battlefield. EA was searching for a way to capitalize on the downtime between these blockbuster releases -- a game which would be relatively quick and painless to create, while still standing up to the quality standards set by their previous releases. Thus, the idea for Battlefield 1943 was born.
Battlefield 1943 producer Patrick Liu explained the studio's unique design philosophy while making the game, which boiled down to "make the game as long as resources last." They maximized the amount of content they produced under this strategy by settling on the somewhat smaller scope of the game early, and focusing on recreating the Battlefield experience to adhere to that scope.
Some decisions made under this philosophy include making ammunition and health auto-regenerate, cutting down on tiresome resource runs back to your home base. This decision led to others, including the removal of the medic and engineer classes. It also let them focus on perfecting a handful of maps and gametypes, which, while iterated from previous installments in the franchise, also saw major adjustments in 1943.
The result was a project developed by 15 series veterans at once, at one-tenth of the cost of a full DICE game, which broke day one, week one and month one downloadable sales records. It's no surprise that Liu expressed interest in developing more "games of this size and scope" -- when handled correctly, it sounds like a miniature entry in a major franchise can be quite the profitable cash cow.