I'd argue that GH won over Bitbucket because of two key factors: 1. It wasn't developed by Atlassian, who at the time had a reputation for building more unwiel

I'd argue that GH won over Bitbucket because of two key factors: 1. It wasn't developed by Atlassian, who at the time had a reputation for building more unwieldy tools (Jira, anyone?) and had a weird, awkward feel. The fact that Git had gained near instantaneous traction and Bitbucket needed you to learn Mercurial made it a near non-starter. 2. GitHub's model ("Social Coding") and zero-effort force amplification made it just the right wedge. Git had terrible tooling on the frontend and GitHub providing "Just enough" tooling around the server side while also providing the right kinds of tooling (webhooks, enterprise-ish features, click-to-fork, a very good PR path, etc) made it easy to use Git. Mercurial might be the "superior" tool from certain standpoints but Git had a few tricks up its sleeve that made people like it: * Written in C. No extra runtimes. * Modular construction: `git-slap` is immediately available as `git slap` like a native tool. * Performance of Mercurial was bad on massive codebases and slower machines. I mean terrible. once you hit 500KLOC or into the 2MLOC, a simple merge could take minutes if not tens of minutes in the old days if you weren't on a fairly modern (2005-7ish) machine. If you'd kept your slightly older P2 laptop around, you were absolutely roasting under the weight of what took Git mere seconds.