A lot of it has to do with a culture shift. He wants to create a culture where players trust coaches that they know what is best and their decisions will help them grow as athletes and people. And you're either on board or your not.
Now these young athletes know they are the true moneymakers in this gig and they feel empowered and are tired of the dictatorship that many coaches like to run. They want attention, individuality, glory, freedom to do and say whatever they want to whoever they want. Kirk has to choose. Adjust to that culture change or be gone.
Bobby Knight was an elite, respected coach in mid 1990s. He refused to adjust to changing culture, got fired, and was meh at best at Texas Tech.
It happened to other professions long ago. Look no further than public school classrooms. 15-20 years ago teachers were still authority figures in their classrooms. Now educators are basically salesman/mental health support/mediators. They have to sell parents that what they are doing is right because without parent support teachers are basically powerless. Support students with growing mental health issues and mediate the conflicts that arise daily.