The Horned Frogs coaching staff was aware of Michigan's antics after being warned by several coaching staffs. And they had a plan to counter it in last season's College Football Playoff semifinal win.
You're telling me that Michigan's sign-stealing was common knowledge among Big 10 coaches, but none of them thought to use that knowledge to feed them misinformation?
I'm not sure whose incompetence is worse, Michigan's for running a sign-stealing scheme so blatant that their whole conference knew about it, or the rest of said conference for not being able to take advantage of that knowledge.