You guys are all missing the point, the problem with JMI is not UK's media rights, it's the players'.
Like Matt Jones said, part of this deal involves Amazon directly paying the Duke players to promote these games, as well as other Amazon services, and gets paid endorsement fees that is NIL outside of the school's $20 million allotment. Which means there really is no limit to how much Amazon can pay them, if Duke say chooses to lower their fee, in favor of Amazon transferred some of that into direct payment to players. The NCAA can't say anything because Amazon is so huge, and their services are global. No amount of payment from Amazon to a player, can be red-flagged by the NCAA for not being a legitimate marketing deal.
And this is where JMI comes in, because their deal with UK requires all players to sign over their NIL rights to them. So Amazon can't pay these players directly, they would have to negotiate with JMI, and JMI is not required to share those payments with the players, because their deal is that after they pay the players the agreed amount at the beginning of the season, that is all the players are entitled to. JMI can go out and make extra money on those rights. Because they are putting the guaranteed money up front, they can turn a profit on securing additional marketing deals with the player's rights. Any big time player who is capable of getting their own deals will never sign a JMI contract. Only players who aren't well known enough to get those types of deals will. Which is why UK can't get any stars or top recruits, they only get complementary type players.