Mercurial and Bazaar also showed up at around the same time as git, I think all spurred by BitKeeper ending their free licenses for Linux kernel devs.

An interesting shot to the foot, that one.

BitKeeper was a proprietary version control system that somehow (and with a lot of controversy) ended up being adopted by a big chunk of the Linux kernel developers, while others were adamant against it.

In any case, they provided free licenses to Linux devs, with some feature restrictions (including not being able to see full version history) only available for premium clients, while Devs who worked on open source competing systems were even barred from buying a licence.

When someone started to work on a client that allowed access to these locked away features, they revoked the free licenses, and a host of solutions started being developed immediately. Linus Thorvalds himself started work on git, and that eventually got adopted by the whole Linux ecosystem and, nowadays, the world.

As for BitKeeper, it's been dead for years now.