Youth + never been told "NO" because of supreme athletic gifts + huge infusion of cash + thinking you're invincible = bad decisions. Not at all surprising, TBH.
To me what is truly sad is that this young man had NO ONE in his life that was willing to sit him down and explain the world to him, even just the Readers Digest version. Something like, "you know, Dwayne, you have more God given ability to throw a football than all but maybe 75 or so people ON THE PLANET. You've been given millions of dollars because of that fact ALONE. Work hard at being a quarterback and you'll end up making tens, if not hundreds, of millions of dollars more. You don't have to be a saint in your personal life, just don't do anything publicly that your mother would want to see on the front page of the paper."
Now, if someone DID have that conversation with him and he ended up in his predicament anyway, then that's on him but again, given his young age and the other factors I mentioned above, it is not a huge surprise. Hopefully either a) someone talks with him b) he matures and/or c) he gets his head out of his arse, or some combo of those things happens because he clearly has some talent to play the position.