I guess I'm supposed to be shocked.
"Oh wow, Indiana, which hadn't beaten Michigan since the 80's, has now in fact done that specific thing! How did this ragtag band of Hoosier misfits pulled off the win against the mighty Wolverines? Reveal your secrets, you wee underdogs!"
Here's how: the Indiana Hoosiers are much, much better than the Michigan Wolverines. They're better coached, more rounded offensively, have a more talented quarterback, and don't suck in ways that Michigan very much does. I didn't watch the game live because I had better things to do, but when I got around to it on Sunday I was struck by how much the Hoosiers' 38-21 win looked like Ohio State beating up on Rutgers at home.