They aren't entering into deals to play football. They are licensing their name, image, and likeness in exchange for money. Just because they go play football somewhere else doesn't mean that the first school loses its contractual rights to use the name, image, and likeness. As you said, they aren't employees, so these licensing agreements don't come with non-compete type provisions. They just say that school 1 has the exclusive rights to use the player's name, image, and likeness. If this went to court, UW would have sought an injunction preventing LSU from using Williams' name, image, and likeness, which by default would have prevented him from playing for LSU if UW won. The license agreement doesn't just go away.