[frodowtf]

This.

And maybe I overread it, but why did he start working on core-js fulltime when there was absolutely no financial compensation in sight? It's like investing all your time in a startup that you know will never pay off.

He should have just left the project as is. The state of JS is not his fault. He is not responsible for fixing it. Once the incompatibilities become too annoying, somebody will take care of the project.