Now they are free to spend their (free) time on what they want. When most of the core contributors where payed by Mozilla, they could not chose to eg. "focus on

Now they are free to spend their (free) time on what they want. When most of the core contributors where payed by Mozilla, they could not chose to eg. "focus on web compat", hence they went on something you consider useless, but that kept the project alive. That allowed a few other things to be done like the re-write of the parallel layout. Of course we can't know for sure what would have happened if they refused to work on VR, but my gut feeling is that this would not have helped the project.