Git already had momentum before GitHub became popular. And yes, it is absolutely Linux and other high-profile projects that ensured its success in the OSS world. Claiming that Linux having used a different VCS before git means that Linux's use of git doesn't matter is really odd when git was developed for the Linux project.

It sure had momentum. As did a bunch of other distributed VCSes. If you were a party to voting what VCS to switch to for some of those high-profile projects, I'd very much like to hear about it.

In GNOME, a decision was delayed and bzr and git were pretty evenly matched.

Linux has previously used BitKeeper, but that didn't make it "win out", just like it didn't do so for Git. Sure, it wouldn't have existed if there wasn't a need for Linux.

I am only pointing out that it was GitHub that helped popularize arguably the worst UX among DVCSes: I don't hear people say "your free software contributions portfolio" — they'll just say "your GitHub profile".

bzr lost because it was poorly-architected, infuriatingly slow, and kept changing its repository storage format trying (and failing) to narrow the gap with Mercurial and Git performance. Or, at least that's why I gave up on it, well before GitHub really took off and crushed the remaining competition.

For my own sanity I began avoiding Canonical's software years ago, but to me they always built stuff with shiny UI that demoed well but with performance seemingly a distant afterthought. Their software aspirations always seemed much larger than the engineering resources/chops/time they were willing to invest.

Sure, that's a fair point as well (though bzr came out of GNU arch, which didn't originate at Canonical, and it was finally redesigned into something good at Canonical — not a knock on arch either, it was simply early).

The question then becomes: why not Mercurial which still had a better UX than git itself?

My point is that git won because of GitHub, despite lots of suckiness that remains to this day (it obviously has good things as well).