I worked at Mozilla during this time, originally on desktop and later on mobile. I think the fundamental problem then (and still a problem today) is that Mozil

I worked at Mozilla during this time, originally on desktop and later on mobile. I think the fundamental problem then (and still a problem today) is that Mozilla only ever had the budget to do Desktop XOR Mobile. Not both. They basically mortgaged Desktop Firefox to build Firefox OS, but when things didn't pan out was quickly as they liked, they had to revert back to Desktop to save the cash cow. After that experience, upper management became averse to mobile, to the extent that it was (and probably still is) very difficult to get resources allocated to mobile implementations of Gecko features that are supposed to be cross-platform. In practice many of those features are never implemented with mobile in mind.