Mozila will never have the marketing firepower to pull off such a boycott.

Apple disabled Flash for "security reasons." You can certainly read in politics, but the reason they gave was that it was the #1 attack vector on Macs and they had no way of securing it. And more importantly, nearly everybody else was on Apple's side in this fight. Other browser makers had problems with Flash too. Mac users largely hated Flash because it had terrible performance on that platform. Even Adobe was cooling off toward Flash as it became more and more clear that it wouldn't work on mobile platforms.

Mozilla's position here is not at all similar to Apple's position then, so their options are not the same.

The cost to the user of switching off Apple hardware is much greater than the cost of switching from Firefox to Chrome.

A few years ago there was a cost involved for switching to the iPhone. The only reason why you see this the other way round is that "no Flash" is now established (at least for mobile). On the other hand: no DRM in browser cannot be considered as established - so we are at the same point where the iPhone was some years ago.

Apple also did this for performance and usability reasons. And when Apple did it, there were no smartphone alternatives that provided a sufficiently good Flash experience.

And before you say Android had Flash, I had an Android device that could run Flash in 2011. It was a pretty useless feature.

Saying that Apple "disabled the possibility to install a Flash plugin" implies that that possibility existed at some point. Support for installable browser plugins has never existed on iOS, so there was never anything for Apple to "disable".

Adobe offered Apple an iOS port of Flash and Apple had Access to beta versions of ports. Thus Apple could have enabled the option to install it by default or as option. But for political reasons Steve Jobs/Apple decided differently.