Apple wouldn't let Firefox onto the iPhone. Pretty big writing on the wall, there. Turns out it's really hard for a sub-billion-dollar company to succeed with a mobile OS, though, which is why we only really have two left. (Even Microsoft couldn't swing it)
> Mozilla caves to Widevine DRM: 2014
Shipping the only major browser that can't play movies, cool cool cool.
> Directory Tiles: 2014
Nearly everything on the web visited with Firefox is funded by advertising. The new tab page is one of the least obtrusive surfaces in the browser that still gets seen. Seemed worth a shot to try building an ad stack in that space which tried not to surveil.
> Pocket acquisition: 2015
Discovery on the web is hard. Maybe that's a job for a browser? Maybe folks will pay for it? Maybe it can pay folks on the web?
> Firefox Focus: 2015
Privacy seems like a good idea. Maybe folks would like a browser that focuses on that?
> Cliqz experiment: 2017
That's Brave Search, these days. Lots of folks seem to like it?
> "Looking Glass" Mr. Robot sponsorship: 2017
I don't know the whole story there. IMO, looked to me like some earnest folks tried to do something fun but rolled a 1 on the d20 for a critical fail. Footguns abound.
Not saying all the above were handled with perfection, but I was there for all of them and there were good folks doing things that made sense at the time. Hindsight is 20/20, I guess?