A guy like D. Hall who is a very good college player without a very good chance of playing in the NBA was exactly the kind of kid you wanted before.
That kind of kid would stick around for all four years, provide leadership, set an example of hard work, etc. They were very unlikely to transfer because they were getting a good education in a good environment, playing ball, chasing a championship, and even if they could transfer to a Duke or whatever there really wasn’t any reason to do so, as their playing time would likely go down, and their already meager NBA chances would not go up. The end goal for them would be to get a good degree then play overseas and make some money there.
With NIL their best chance to earn money playing basketball isn’t after graduation, it’s right now. The sums people are getting paid are often 10x or more what they are likely to make upon graduation: Khalifa is reportedly getting $600k to redshirt.
To make 600k a year as a 20 year old kid is life changing money (assuming you are smart about what you do with it). It gives you a MASSIVE head start in life.
With no rules and no restrictions the rational thing to do is follow the money. That’s the way the game has now been setup. This is especially true in basketball, even more than FB, because the NIL value of an individual player (other than a QB) to a team will always be way higher when you only have 12 on the roster and only 5 play at a time.