People use it in those places because it's free, not because it's particularly good. In the case of smartphones, the underlying OS is completely irrelevant. There's no serious reason that FXOS or Android couldn't run on top of a different OS. Further, a number of the spaces you mention aren't generally a good fit for a monolithic kernel archetecture, but get saddled with Linux anyway because it's free.
Without Linus to create Git, you probably wouldn't have had communities like GitHub emerge nowadays (or they would have tried to built on much less optimal technology
Git still sucks, it just happens to suck less than the alternatives. You don't need Linus or some other auteur to get a crummy VCS. It's entirely possible that some lesser known or unknown alternative would have risen to prominence but was overshadowed by Git (or simply dropped by the developers).