Proof: what are the other source management softwares? (Don’t mention Mercurial, that’s cheating).
Also for Linux, it’s down to the license and history. Linux isn’t a bad investment because all commits directly to the kernel are given freely to all. And it’s not Unix. It doesn’t have the stain of AT&T and their sue happy ways. Also Linux dominates all computer markets except for user desktops. Servers, phones, application specific utilities, etc.