I blame how things turned out more on Mozilla being distracted and forgetting about their own user base, to be honest.
The fact that it made the browser itself impossible to monetize to fund development was a part of it. They were an antitrust insurance to Google and tried lots of stuff to improve its position. Granted they failed, sometimes quite spectacularly, but I still drive Firefox for personal use.
The money earned with Firefox should have gone to Firefox but went to vanity projects instead. Firefox OS, Mozilla Social, Firefox Send / Persona, acquiring Pocket, etc etc. And all of it failed.
Nevermind the controversies of silly ad campaigns and CEO salaries and whatnot.
Mozilla should have just reinvested all the money into Firefox. Heck, they couldn’t even finish their rust-based rendering engine.