I have a fairly good, fairly reasoned idea as to why he'd commit suicide now. He was recently found not guilty in a double murder. Great, he'd already been convicted of murder once anyway.
Except he hadn't FULLY been convicted. His case was on appeal and because of a very old and obscure law in the Commonwealth of Massachusetts he's not officially and fully guilty until the appeal plays out. Technically, he just died an innocent man because under that law if the defendant dies the case has to go back to the beginning, ie not guilty.
Aaron Hernandez played in the NFL and it's my guess since he's not guilty of anything he gets some kind of pension payout for his family or friends, really the only thing he had left to work for. If the appeal was dismissed and his appeal thrown out he'd get no chance at anything.