Like you at first I did not understand, their focus is the open web, not that much the browser.
I think (we could actually check Mozilla meetings notes to know for sure) that :
- They saw that mobile web/internet would be where most of the traffic in some years.
- They saw most of the mobile internet was webkit prefix specific.
- They also saw they would not be able to provide Firefox by default on most phones, and people were unlikely to change the default browser.
- They finally saw that internet was moving to use "apps" in walled garden silos platform control by 2 companies (3 if you account for MS) instead of an open specced web.
They started FirefoxOS to provide an alternative option to users when buying a phone that is focussed, streamlined and was fulfilling Mozilla mission in providing a better open web.
FirefoxOS 1.0 was a basic smartphone OS really great for a grandpa moving to a smartphone. I could not tell such a thing for the Samsung Galaxy S3 The latter the versions, the better the features. Last FFOS version before being killed was actually fcking awesome (not perfect yet but it was close to be able to,some more month and that would be it) thanks to the webextensions being implemented OS wide. This puts the (power) user in control, really.
I found this enough appealing ( also after I've done some small web apps and deployed them to my FFOS phone, it was just sooooo simple) to look for a big and hopefully powerful phone (I just had this toy FFOS for less than 50EUR) with the latest FFOS on it, instead of my android phones I had since the G1.
But they killed FFOS right when I was searching for this next phone.
I was ready to pave the way and really write the apps (and/or webextensions) I was not finding yet to my tastes for a primary phone, it was not that hard, actually really easy for a web developer compared to even any webview based app. I was even OK to write my own keyboard for matching my expectations regarding it( not that the original was really bad, but it was no great either, but for the multiple keyboard switch system). I was eager to try to write the code (and waiting for the API on bluetooth was complete enough ) for conversing with my bluetooth devices ( including my Pebble ), and I was happy any website could actually do it once a simple JS lib published on npm would do the hard part of the job.
But when they saw the market for small priced device was invaded by Android devices because the cheap phones spec became good enough, they knew their inteneded market was never getting grounds, so they stopped it. In fact, once at this point they should have IMO switched and target the middle-high end power user, which would have gave them a new kind of influence, and access to actual hacker needing apps and able to write them.
But this was not that much an option as they wanted to get rid of the way they were financed at 90% by Google, in order not to be locked by it, notably to be able to focus on privacy like they did since (and containers are fcking awesome, thanks guys :), I have my own walled garden for you, web, I the user ! ), and they would likely lack of money to do this switch and the needed deals to achieve that.