Earlier quoted context omitted.
I don't quite get why the Flash plugins were do slow on mobile. On Windows desktop, Flash was much faster than other NPAPI plugins. Most other plugins froze the whole browser for a second or so (Java even longer), while Flash didn't do that. And at the time, early native "HTML5 replacements" for Flash ads/games were actually slower than Flash.
Flash was software rendered almost exclusively. It also had quality options that let you scale the software renderer down a whole lot. But it still required a beefy CPU to push all those pixels. On mobile, you don't get a fast CPU - you get hardware accelerated EVERYTHING. Everything has to be done on GPU. Hell, iPhones still have dedicated JPEG decoders in them. And vector rendering on GPUs is a pain to do, even mor…
To be fair, on the single 100 mbit link the site used to be on, for new things being posted, that would be historically accurate...