so it is a myth that pro head coaches won't be successful as college head coaches?
How about the folks in the business recognize the enormity of the differences in the business and few make moves and generally it is those out of career options at the pro level? And that explains Carroll, Mora and for that matter the latest to make the move, Lovie Smith who pretty much wasn't going to get another shot at a pro head coach role.
The evidence that does exist shows that it is not a myth and strongly indicates that it takes a rare individual to make it work.
Overall, about the only guy(s) (in the last 25-30 years) who have made the flip in terms of being successful at both levels is Carroll and possibly Harbaugh but his experience in coaching was mostly at the college level and he had a long career in the pros so he has ample knowledge on both sides. Find another guy like that and it can happen. And by the way, Saban and Mora could hardly be classified as even average head coaches in the pros.
I have a better chance of winning the Powerball than the next coach at ND being a truly successful NFL head coach who has no recent exposure to college coaching.