I'm pretty sure there are several VCSs written in C that are left in the dust by Darcs, and keep in mind that git adoption got a head start from being promoted by some guy named Linus Torvalds. (Perhaps you've heard of him?)

I don't see your point - there are many, many things beyond the choice of language that determine the eventual success of a product.

You might want to read: http://www.paulgraham.com/disagree.html

I think a lot of this story can be explained by looking at the size of the contributor lists:

http://git-scm.com/about http://wiki.darcs.net/DarcsTeam

Git is very polished because a lot of people have put a lot of time into it.