First, I'm not a Gruden lover. Second, I don't dislike Dooley, I'm not uber confident in him as a coach on the sidelines. With that out of the way...
Lane Kiffin was was 5-15 (.250) when he was the HC w/ the Raiders. Obviously, he never made the play-offs. Gruden, with the Raiders went 40-28 (.594), made the playoffs twice. They were both, at the time of their hiring, the youngest coaches in the NFL. Both considered to be "genius" offensive minds.
Davis couldn't wait to get rid of Kiffin. Davis, on the other hand, demanded a lot from the Bucs to release Gruden from his contract. So much so, one might believe Gruden's demise with the Bucs was in part due to the price the Bucs paid. 2 first round picks, 2 second round picks, spread over three consecutive drafts. They also paid Davis $8 Million.
In that context, it's easy to understand why Gruden's first team went to the Superbowl and then declined. He took over a Dungy team that was not reaching it's potential, not meeting expectations, but the talent was there. After that, free agency, coupled with no draft picks, and lack of money to replace free agents...well.
As for Saban, he couldn't hack the NFL, same with Spurrier. Both of them had done well in college and wanted to test themselves in the pros.
I don't know how Gruden will do in College if he decides to go that route, but I know this...Saban isn't coming here, Spurrier isn't coming here and if you look at the top 25 right now, you gotta go down the list to around 10 and below for Strong, Peterson, Holgorsen etc...Doubt we could get Peterson, Holgorsen, Patterson...take your pick...Strong or Gruden...Tuberville or Gruden...Dooley or Gruden?