So Pepper Rodgers had a career 20-22 record at KU, I guess I see why he would be in consideration for greatest coach of all time. 
Led KU to a 9-2 Orange Bowl season in '68 and then took a job at UCLA. His career record was 73-65.

Followed up that 9-2 season with a 1-9 season, then another below .500 season, then left KU with a below .500 record overall, and apparently the title of greatest KU coach of all time.