Here is how understand NIL works using a real world example:
Back in 1998 and 1999, José Lima was a starting pitcher for the Houston Astros, winning 37 games in two seasons and was selected to the 1999 National League All-Star team. This was so called "Lima Time" rocking and Casa Olé (Fresh today, every day!) signed Lima to a deal in which he appeared in television commercials promoting the fine Mexican cuisine and ambiance offered by the Houston area restaraunt chain. In 2000, José's heat lost its spice and he had a league worst 6.65 ERA and gave up 48 enchiladas. The Astros traded him the following season. Casa Olé paid him to advertise for them based on the idea that his successful pitching would cause fans to choose Case Olé for their fine dining needs and purchase more tacos, burritos, green sauce and the like. Once he was no longer an effective pitcher for the Astros, his value to Casa Ole deteriorated like old queso. His was not paid to play even if his value was derived from his successful play.
In my mind, college sports NIL is the same. Being an athlete creates value but the contract does not require athletic performance. A specific player is valuable to local business seeking an NIL partner while a member of the local team. Once that player disassociates themselves from the local team, then value goes away.