OK, I'll explain.....sorry for the long-winded response, but I'm long-winded.
#1 - It's absolutely essential for competitive balance. Hopefully I don't need to explain why that it is the case.
#2 - Coaches, admins and staffers are professionals that almost by necessity need to move from job to job to climb the "corporate ladder" if you will. Look at GP's career path before he got to TCU. The vast majority of these coaches have paid their dues to some degree by constantly moving their families around, etc. It's not like all these guys have made $3M plus and cashed in buyouts their entire careers. College kids are theoretically supposed to be student-athletes, trying to convince me that a kid going to 2-3, even 4 different universities in 5 years is ultimately beneficial to the kid in the long run would be hard, unless the world is upside down. If college players think it's unfair that coaches get to move around and they don't, they can go be a coach after college.
#3 - Players pick schools for any number of reasons....could be location, could be a girlfriend situation, a recruiter, an O or D coordinator, could be a Head Coach. Heck, it could be for academics. Simply making their immediate eligibility elsewhere tied to the Head Coach is dumb, when it very well could be a case where he chose a school in spite of the Head Coach. Besides, what if a coach doesn't move on but is fired? Same rules apply?
#4 - This doesn't fall into the same category as 1-3, but part of playing sports at a high level (at any level, really) is occasionally being in a position to have to play for a coach who isn't your handpicked guy, or it might even be a guy you don't like. Players at all levels are required to do it all the time (if they in fact want to play). If a high school coach leaves to take a college job should the UIL just let all those kids that played for him go wherever they want? Of course not.
They took a situation where kids weren't allowed to make money on the side off their name, image and likeness and made such a massive overcorrection to where it's now a completely ridiculous, unsustainable structure for a "team sports league", or whatever you want to call it.