Because GitHub offered free git hosting, and heroku came along and offered free hosting that was pretty much point and go.
Combined, you all of a sudden went from needing a sysadmin and two servers (this was pre containers), and the sysadmjn skills to operate SVN and your web app, to “it’s now free and it auto deploys when I commit”.
This war was over around about the time I started, but my take on it is that it's all a bit intermixed and Mercurial lost because bitbucket caved and did git hosting [2], but git won beacuse of github and heroku [1][2]
Bitbucket and GitHub started around the same time. GitHub executed better. And the Ruby community adopted GitHub early. Comparisons around 2010 said GitHub's UX and network effects were top reasons to choose Git. Mercurial's UX and much better Windows support were top reasons to choose Mercurial.
Because GitHub offered free git hosting, and heroku came along and offered free hosting that was pretty much point and go.
Combined, you all of a sudden went from needing a sysadmin and two servers (this was pre containers), and the sysadmjn skills to operate SVN and your web app, to “it’s now free and it auto deploys when I commit”.