Neither was John Harbaugh. There are many different ways to skin the cat.
Lots of guys that have been NFL or major college OCs or DCs have failed. There is no one size fits all solution.
You vet out the best guy for your team through the interviews, not just the black and white past job titles, especially when talking about a coach that’s been in the league this long and also seems to always get instantly promoted to Assistant HC/Associate HC at his stops and players seem to look at as a HC type figure.