I think Curry just mistakenly thought he was at the top of the mountain.
Back when he was in college, you would hear all this stuff about how hard he pushed himself, how much he worked, etc. I don't think that was fluff. But the problem is when you drive yourself like that eventually you mentally wear out. I used to call it "six sprints and a collapse".
The hard part about goals is that when you focus on them like that, drive yourself for years to get them, and then finally reach them - what next? There is an understandable inclination to stand on top of the mountain and just feel like you made it. He worked for years to get to the NFL and he finally made it.
The problem is that once you get to the top of whatever ladder you are climbing, you usually are faced with another ladder that is even harder to climb.
Either the competitive drive has to be internal (like a Jordan) or if it is fixated on a goal like that it is just easy to be exhausted. And once you put in years of work like that it is understandable to feel you have a right to relax and enjoy the fruits of your labor.
I don't think the guy was a bad guy. And if you watched him in college it is clear he could be a great player, I think his heart just wasn't in it. He himself said his goal was to lift his family up from poverty - well he did that. So it is easy to understand, even if you don't agree, that after years of doing nothing but eating and breathing football...he decided to actually live the rest of his life. The problem is that doing that made him average, or worse, and so he lost his value as a football player.
Maybe he realizes what he misses about the game or maybe he misses the paychecks. I don't wish any ill on the guy, I hope he succeeds because we don't need him to fail for our team to be successful.