I would think this was to be expected, but surprising still....It's been 4 years since he's been down, he has a life sentence. It gets harder everyday for someone with that LWOP to process it, and I'd imagine he's been spiraling mentally for years, whether we knew it or not. The gang fights and posturing is just a coping mechanism. I'd think it just eats away at you over and over again, until you can't take it. A lot of these inmates are delusional, and clinging to appeals or God, that they will be saved. For Hernandez, he'd probably had enough. I would have done the same thing. Life just isn't worth sticking around for at that point.
Also, murder by hanging would be less then usual in prison, esp someone like Hernandez, NFL player, solid, able to fight, he'd have been stuck, or thrown off a tier or something.