Sorry for the title.
Lloyd Carr is unquestionably a loyal man. Loyal to his friends, his players, his athletic director. This is a good thing, generally. Unfortunately, his loyalty to Mike DeBord was misplaced and ended up tarnishing his legacy. Mike DeBord may be a good person, a worthwhile friend, but he was not a good offensive coordinator for Michigan, especially not the last couple of years.
In the end, Lloyd Carr was loyal to a bunch of relatively weak assistant coaches. Debord is the most obvious example, but Fred Jackson (running backs coach and "Associate Head Coach"-huh?) has been on the staff forever. Weak assistant coaches are death in college (or pro) football.
In contrast with Lloyd, Bo Schembechler had tons of very strong assistant coaches. Numerous of his assistants later went on to be successful head coaches at the top level: Don Nehlen at West Virginia, Bill McCartney at Colorado, Gary Moeller and Lloyd Carr at Michigan, Cam Cameron of Indiana and the Dolphins, and these are just the ones off the top of my head. Oh, and Les Miles too....
Unfortunately, Lloyd'd assistant coaches just weren't as good. He's obviously not the first person to let personal loyalty overshadow incompetence. But it's a shame that it will impact his legacy.