I'm not sure I agree with that analysis. Seems like you are using the 90% of athletes that screw up millions of dollars of instant income to be indicative of the entire group. I'm sure there are number of instant millionaires that aren't athletes that also go broke, but I don't think it's anywhere close to 90%.
I've seen sources claiming that
70% of lottery winners squander their winnings within a few years. Of course, there are many factors to consider, but it's out there.
On top of that if you include the guys that just become extremely wealthy fairly quickly like the Steve Jobs, Bill Gates or Mark Zuckerburgs of the world, that number drops even lower.
Steve Jobs, Bill Gates, and Mark Zuckerberg are not "instant millionaires" in any useful sense of the term. Those are people who built and grew a business, advancing through many stages of increasing wealth in the process; contrast this to a lottery winner who goes from food stamps to multimillions with one check, or an NFL draftee who goes from broke college student to ultra-wealthy by signing his first contract.
I think there is something to the fact that these guys are not just getting rich, but that they are also quite young, immature and feel very entitled typically because they are athletes and have always been treated "special" because of their ability to play a game.
I think it has less to do with entitlement and more to do with a simple lack of financial savviness. I certainly don't think lottery winners feel "entitled" (other than the entitlement created by winning millions of dollars), and they still go bust.