[iSnow]

>that they have the most popular browser, but they have a browser with enough users

Well yes, but they arrived at this by having a vision what a good browser is at a time when browsers were abysmal. They didn't arrive there by just wanting an open-source browser. Yes, there was a network effect at play too (everyone "optimized" for MSIE), but they were able to bootstrap their user base with the tech-savvy who were fed up with the horrible HTML/CSS/JS support browsers of the time offered.

They did not have that vision with FirefoxOS - they wanted to secure a foothold in the mobile market, but had no compelling idea on how to gain that in the face of Apple/Google. Similarly, disliking Zuck is a a really bad reason to pour energy into yet another open social network.