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]

[1] https://www.koyeb.com/blog/herokus-free-tier-legacy-the-shou... [2] https://blog.gitbutler.com/why-github-actually-won/