Weren't most of Oklahoma's most explosive offenses under Long as OC?
After the 2001 season, Long was promoted to Oklahoma's offensive coordinator position. Oklahoma won the Rose Bowl following the 2002 season, and in 2003, the Sooners set a Big 12 Conference record by averaging 51.5 points per game.
Long became available for the 2012 season when Turner Gill was fired at Kansas. Kansas didn't score much. Both took a death sentence by going to Kansas. Gill was probably a pretty good coach and was HC at very tough places to win.
I believe Long was actually Co-Offensive Coordinator at OU. WAS Mangino the other Co in the duo? If so, he may have proved out to be the better of the two, since he actually won at KU AND Long didn't at a lower level.
He MAY be a pretty good OC, but he didn't have a lot to work with at KU. I would debate whether Turner Gill was an above average high level D1 coach. He was absolutely horrible at KU, and didn't recruit half the talent Mangino, who is three times the coach that Gill is, did.