> when service workers and PWA's became mainstream, and also the new rendering techniques from servo are integrated into gecko
If service workers were invented, PWAs were a thing, or Servo had been built, Mozilla's actions around Firefox OS would probably have been much different.
What really killed Firefox OS was the lack of ecosystem. VP of Apps Rick Fant put all the emphasis on apps for Firefox OS instead of Firefox for Android. Firefox OS could run any app built for F4A, but not the other way around. Why would I, as an engineer, write an app for a device that I can hardly get my hands on, running an operating system almost nobody uses, with customers who (in many cases) don't want to pay $0.99 for an app, using APIs that don't work on anything else, and translate it to a language you don't speak? There were millions of F4A users at the time, and Mozilla made no effort to get folks to build for it at all. A real shame.