To be fair the "shortcomings" that spurred it on mainly were the Samba guys (or just one) reverse-engineering Bitkeeper causing the kernel free license getting pulled, which caused Linus to say "I can build my own with blackjack and pre-commit hooks" and then he did, addressing it toward his exact use case.
It gained tons of popularity mainly because of Linus being behind it; similar projects already existed when it was released.
Mercurial was there, was better and more complete.
Too sad it didnt win the VCS wars.
When I tried both at that time hg was just really slow so I just adopted git for all my personal projects because it was fast and a lot better than cvs. I imagine others were the same.
I went with bzr mainly because it had an easy way to plugin "revision" into my documents in a way I could understand and monotonously increment.
hg was slow though I don't know how bzr compared as I was using it pretty light-weight.
Mercurial and Git started around the same time. Linus worried BitMover could threaten Mercurial developers because Mercurial and BitKeeper were more similar.