The reality is that mobile OS that will offer free IOS/Android wrapper for apps that actually works out of the box will win the market. This way from day 1 there will be enough apps for users to consider switching.
It didn't work; third party developers saw that a Windows app could serve both the Windows and OS/2 markets and focused all their energy on their Windows app, usually not bothering to write an OS/2 version at all. The result was that Windows' big moat -- its application library -- actually got deeper. IBM's big plan to kill Windows ended up cementing its position as a dominant platform.
What makes or break a Mobile OS is the availability of the key apps for the market you're going after: whatsapp, FB, Twitter, etc. (that varies based on the region).
Was that ever released? I saw it on Mozilla employees' dev phones, but nowhere else.
You likely saw the other attempt using the J2ME-in-js implementation: https://github.com/mozilla/pluotsorbet
That was too slow and never shipped in commercial devices either.
MS is doing somewhat the IBM thing with their Linux for Windows. I've been curious to see if that would have the same result for them that it had for IBM.