I never kept tabs on the development effort on neither VSCode nor Sublime Text, but it was always my impression that much of the power either editor has comes from 3rd party extensions rather than the editor core. As such, I believe it was the hype around Atom and VSCode that drove people to write extensions for them, leaving ST behind.
>but it was always my impression that much of the power either editor has comes from 3rd party extensions rather than the editor core
A lot of it, yes. But VSCode also invests a lot in core functionality (in what in other platforms would be plugins). The Git integration is one such example -- or the ability to debug Chrome in it.
