Adobe expecting Flash authors to make versions optimized for mobile wasn't particularly crazy though, was it? That's exactly what browser makers expect mobile site developers to do. A non-mobile optimized site mobile is an awful experience.

W.R.T. compositing, browsers took a long time to move to even just GPU based compositing, and full GPU based rendering took longer still. Certainly, if Flash hadn't been killed off so prematurely it seems reasonable that either they'd have done the work to keep up, or users would have organically abandoned the platform.

Indeed, you make a good point that it was really a fight over forcing devs to use Objective C and nothing else. Flash was just roadkill in that fight.