Arguably, success as a professional coach is substantially more objective and less subjective than many professions. Professional sports analyze everything. Statistics is huge both for the fans and the teams. Is the team winning? For colleges especially, you have annual turnover in student ranks so more in-and-out of players than NHL, NFL, NBA, etc etc. That's got to be tricky to manage. You have to attract talent to the institution and develop it when there.
So the simple fact is these coaches are able to demand these packages (and get them!). Someone out there has to write the checks and believes the performance and outcomes justifies the cost, that they are "worth it".