He wasn't supposed to be alone in the cell. They were supposed to check on him. The surveillance cameras were supposed to work. It's possible this is 3 human fuckups in a row with sad consequences. By which I mean his victims could never see him in court getting convicted. It's also possible that he was killed in custody. We like conspiracy theories. We may never know. Because you would need to be able to prove this. And unless they filmed themselves hanging him, which I doubt they did, then this will take its rightful place among the great myths of our time.

It's also possible he offed himself. He may have suddenly discovered a conscience and developed scruples (low chance). He may have not felt like discussing his pedophilia in open court again and chose the coward's way out (higher chance). Somebody may have pressured him. He knew shit about many of the rich and powerful; the reverse may also be true (highest chance of these three).