Has there ever been a successful NFL head coach that jumped straight from head coaching college teams to head coaching the NFL? I recall Nick Saban doing that leap and it not working out. But I can't think of any others.
Harbaugh was successful at U. San Diego, then Stanford before winning big as the 49ers HC.
Bobby Ross won part of a national at Georgia Tech and the had success with the Chargers including taking them to a Super Bowl in the mid-1990s. He did ok with the Lions also and has a winning record overall as an NFL HC.