Github definitely extended git to a far less technical audience than basic git came from. Emailing patches or connecting to others' remote hosts to pull changes was too much complexity for many customers.

Pull requests, CI platform, authentication that is not PAM etc.

Is that any of that something that cannot be easily replicated?

A lot of work maybe, and required a vision to do so initially. But straightforward work that MS could easily do it, and of course other small companies have replicated it too.