Mozilla doesn't have a real sustainable business model right now. FireFox OS could have provided such model, in fact, its successor kaios is doing very well and one can imagine that in the future, it will be the primary OS of half the mobile users on the planet. 'Feature phones' aren't dead. They provide a cheap alternative to touch phones, are usually more robust, and allowing them to run web apps instead of MIDP st…
It's execution is not actually very good, if "doing well" means quality. I was actually avoiding getting a smartphone for a while, but the rise of kaios-powered phones, at least the ones in the US, drove me to smartphones. Contrary to the promise of firefoxOS/kaiOS, there was no kind of "app store" or other way to install custom apps, it just had the usual featurephone features. What there was, was a phone where every keypress had like 750ms-2000ms of latency until it had an effect on screen, making it almost unusable. It ruined feature phones, at least for now. I tried a couple. It's a pretty terrible product on every US phone using it I have seen; whatever led to it being on those phones, it was not quality.
It may be that KaiOS phones available in other countries (always the target market) are better, and an improvement from what came before. (But why are phones available in the US using it for such awfulness worse than what came before?) I would like to think if Mozilla had stayed involved, it would be better.
The business question of course is how the current (Chinese?) company behind KaiOS found enough runway to get it to market when Mozilla did not. Lowered standards/expectations might be part of it though. But it may not at all, I have no idea the story behind what happened. This thread has people giving their reasons for why FirefoxOS failed... but most of their reasons fail to explain why someone else could somehow take the open source IP behind Firefox OS and have a succesful company which succesfully got it onto phones. What was the difference?