Fundamentally the iPhone sucked. It came out without 3G when every other internet enabled phone had it, and constantly dropped calls in the US for the first 2 years until AT&t upgraded their networks. Android phones could run Flash just fine, it was a selling point for them, at least until the Google app store had enough content.
Android phones could not run Flash "just fine". There was no version of Flash released for any mobile device that was what anyone would call "good".
I was writing Flash-based apps/sites at the time and there wasn't a single device we had in our QA set that we thought was "acceptable" in its performance. It was buggy. It'd crash out of nowhere. It'd consume so much memory that user's apps were force quit left and right. It would kill a battery with a quickness such that we had one customer who had to carry multiple spare batteries just to use the app we wrote for their internal team.
I had an Asus tablet with the Nvidia Tegra 3 chip and 1GB RAM in 2011, it ran Flash sites fine, though obviously not at desktop-level quality. Flash games on on Newgrounds were hit or miss, but mostly because they weren't touch-friendly.
You probably recall that mobile internet in general was far from fluid in those days; Browsers couldn't handle multiple tabs well, and iOS would show an annoying mosaic if you scrolled web pages too fast (before the browser could render the page). I would rather have the option of having something imperfect available, than have the OS vendor lock them out entirely.
