Nah, I remember that time vividly, Github became a thing about a year or two after it was already very much taking the lead.
GitHub became GitHub because git was the winner. There were alternative hubs that supported bazaar and mercurial and whatnot, but git won because for most people, Linus and the kernel team being behind it was reason enough to trust it.
(and I say this as someone who liked hg more than git)
Most people just wanted to collaborate on the platform other people were on, and where the popular projects were, that it used git was just an implementation detail at that point for most I think.
So true. I used Mercurial back in the day and also used Darcs before it, and it helped me realize that the best versioning tool UX that exists is still the one Git provides.
PS: Also CVS, SVN, Perforce, and Clear Case professionally, and gave a try to Fossil. None of them even close to Git usability-wise.