NIL really changes the equation for college guys. For guys that are likely to go undrafted (or even late rounds), they may never make an NFL roster. If you can get some decent $ playing college ball, there is a big incentive to stick around and milk it. For many players, the NIL money may be their best and last opportunity to get paid to play a game.
Before NIL, there was almost no upside to staying (no chance of getting paid, possibility of getting hurt). For better or worse, NIL has changed that.