I don't think Mercurial is particularly low profile. Kiln is built on Hg & there has been good support in IDEs like Eclipse & Netbeans for a while now.
Most of the developers I talk to seem to prefer Hg because of the better Windows support. If we were Linux developers it might be a different story.
You're also missing "Bazaar" which is the real "forgotten DVCS".
Certainly I agree that Linus is a very charismatic guy and an alpha nerd almost without equal so a lot of people would gravitate to Git because of that. Also, the "Creation myth" of Git is very compelling with Linus labouring for 6 days to create Git and resting on the seventh - or something like that. When a product has a memorable story it is easier to gain traction.