I think Hill wants to win. He has one year left, realizes he doesn't have much of a pro future, and probably wants his last year of basketball to be spent at a place where he has a real chance to play for a team that will make the tournament and potentially make a run. I've always felt there are three main reasons why a kid would leave: playing time, winning, and not liking the coach. The first obviously isn't an issue with Jalen. The second is, and who knows about the third. I guess now we have to add a fourth, and that's NIL. If I am Hill and I feel like I can go to a better team AND get paid more, it is a fairly easy decision. But I agree with your point that it is concerning to see guys who are playing big minutes leave. It's one thing to lose guys who are buried on the bench. When a starter who the coach really wants to stay decides to leave, there is something to be concerned about.
I think leaving because "wants to win" is part of the culture issue referenced. Ideally you're building a culture where you want to win and win here. And if you're not winning now, there's a belief you will be winning soon because you're building a program and each player is an integral building block toward that future.
I'm not saying it's realistic for everyone to buy in, but we've had a lot of people decide to move elsewhere. A guy like Jalen leaving is concerning -- he's been loyal to the program, two coaches, and from everything I've heard a great kid in general.
All that said, I'm willing to see how the roster shakes out and it plays out next year. I have my gripes about how things are going, but it's not going to be very productive to do anything but hope for the best for next year -- a critical season for OU hoops.