I am saying what SHOULD happen, not what does happen. Cleaning house when a new coach comes in is very common, particularly with first time coaches. They generally have spent years thinking about exactly what they would do when they finally got their first HC gig, and they want to live the dream. They also often have a lot of favors to repay.
My point is that most first time coaches fail. They don't usually fail because of X's and O's, they fail because they are not ready to be program CEO. There are a lot of great coordinators that couldn't cut it as Head Coach (Ellis Johnson is the most pronounced example of this), and quite a few effective Head Coaches who are weak or worse at the X's and O's. Schiano was a joke as a game coach, but did an incredible job at Rutgers. Mack Brown is abysmal as a game coach, and is one of the most successful head coaches of the last 20 years.
One of my issues with cleaning house is that UConn wasn't failing. Weist took over in mid season, and play improved immediately. 2 of the losses were to ranked teams, and Cincinnati had been receiving votes or ranked for much of the season. We beat a Rutgers team by 11 that had beaten Arkansas earlier in the year, and destroyed a Memphis team that had played tough games against Houston, UCF and Louisville. It seemed like the team was getting better half to half by season's end. There is a lot of room for improvement, but it wasn't like the old staff was incompetent. So what does the new guy do? Clean house.
The message that a house cleaning sends is that his way is more important than the right way. That is how a lot of the players and other people around the program will interpret it, because that is how every organization interprets a house cleaning when the people still there don't think things were going that badly. "Because I said so" is not very effective for parenting or being a manager.
I don't want to make a bigger deal out of this than it is. Maybe Diaco wanted to keep 2-3 assistants, but the others didn't want to stay. We will probably never know. I am only saying that cleaning house is usually a bad idea unless an organization was completely failing or there were ethical problems. We don't have much to go on so far, but I would consider this a first time HC mistake. If he holds the recruiting class together and adds 3-4 3* surprises, then we will have some more to go off that is a little more positive.