You didn't specify a MySQL user, or didn't make one, or something.
Actually, I'm dumb. I had this happen straight after you said.
I tried to switch to lainchan, and that's when stuff broke, and reinstalling wouldn't work.
I'd bet that .installed is still in your root directory, because apparently rm -r * doesn't delete hidden files. So vichan thinks that a database and user is already set up, but it isn't.
Just delete .installed, for realsies this time.