Callahan, Pelini and Riley were/are unworthy coaches for an institution like Nebraska, except of course, when they were actually hired.
Callahan had just coached an NFL team to the Super Bowl (and would go back to a respectable professional coaching career) so suggesting the University of Nebraska was above his station is kinda silly. I don't think Callahan was a good fit, and frankly he needed a place to land after his firing, but only hindsight lets you bemoan his hiring over our preferred candidate, the coveted college football genius Houston Nutt.
We didn't "settle" for Bo Pelini. We wanted him. Many already considered him a Husker from his last stint with the team -- and many wanted him hired back in '03 — and when we got our second chance he was the Defensive Coordinator for the National Champion LSU Tigers, part of a resume that included the Green Bay Packers and San Francisco 49ers. There wasn't much handwringing at the time: Bo was no doubt about to be hired by a P5 program, and we got to claim him as proven Husker.
The year we hired him, Mike Riley was voted the second most underrated coach by his college football peers. His reputation for doing more with less was enough to make him a candidate for HC jobs at USC, UCLA and Alabama. His recruiting reputation was so respected that Rivals called the hiring a huge win for Nebraska. NFL superstars like Kurt Warner, Keyshawn Johnson and Chirs Spielman send their sons and nephews to Nebraska to play for Riley.
None of these guys has worked out. Not at the level Nebraska fans demand. But every hiring was defensible at the time, and if we're applying hindsight, the guy you supposedly thought we should hire in 2003, 2007 and 2014 often went on to post records unacceptable by our lofty Nebraska standards.
The only thing sadder is fans who think the University could cut a check and get Nick Saban or Urban Meyer to jump at the opportunity.
It's not easy hiring a legendary coach.