As long as it's pure speculation, here goes:
Mason: built stability in the program and developed, arguably, the best running game we've had, possibly ever. If he'd have had a defense to go with the O, he'd have had us in a least 2 Rose Bowls and kept his job. Too many blown leads in games we had "in the bag", Wisconsin at the dome, Michigan at the dome, his last game in the bowl game where we blew a substantial lead yet again.
Brewster: a terrible hire, he sold Maturi a bill of goods. How Maturi survived this debacle is beyond me. This set the program back at least 5 years.
Kill: won over the hearts of Gopher fans, especially when Souhan called for the U to fire him because of his epilepsy. Kill could have been Coach For Life at Minnesota had he been able to control his disease. He let his emotions get the best of him regarding his tirade against Fleck. If anyone had reason to be bitter about his departure, it was Mason, and yet Glen has never publicly said anything negative about the U and has remained a positive supporter of the program. Fleck had nothing to do with why or how Claeys was fired, yet Kill was obviously po'd about the way his remaining staff was treated and some of PJ's comments about rebuilding the culture of the program.
Claeys: a great defensive mind but not a head coach at this level. I wish him well. He could not recruit against the likes of Ferentz, Harbaugh, and others in the BIG10.
Fleck: people may not like him because of his constant energy, so be it. Many times he's said that the demographics he is going after is NOT the 50 to 70 year old fan, but rather the 17 to 18 year old kid. The way they finished last season gives me hope that the players are buying into his system and the culture is turning a corner. He has a plan and he is sticking to it. Let's hope that after this year he becomes a target for anyone looking for a new head coach. Then we need to raise the bar and keep him. 8 wins or more this year is my prediction.