There's a smaller piece of good news, too: Oreo has climbed above 1 percent after sitting below that milestone since its fall premiere.
The long interval between Nougat's launch and taking the lead can likely be pinned on the same factors that have dictated Android upgrade cycles for years. Many Android vendors take months to deliver upgrades (due to both their custom software and carrier testing), and stop providing upgrades roughly 2 years after a device launch -- you might not see more than one or two major revisions until you replace your phone.
That pattern might not repeat itself going forward. Oreo's modular Project Treble framework is designed explicitly to reduce the delays for upgrades. It might not dramatically increase the adoption rate for newer Android releases, but it certainly won't hurt. The challenge, not surprisingly, is increasing Oreo adoption. It likely won't see a dramatic upswing until more major smartphones ship with Oreo out of the box, such as the Galaxy S9.