In the parlance of my youth when diving off jetties it was called the "canonball", to tuck your legs in under you and hold them in place with your arms as you jumped. If the cause of death was a broken neck it is far more believable that he managed a proper hanging of himself then that some mafioso managed to break it. Breaking someone's neck requires a lot of force and isn't instantaneous which mean Epstein would have defensive wounds from when he tried to break the hold of whoever did it. Since manually breaking a neck also requires some sort of leverage, since very few people have the strength to actually do it, that'd necessitate a struggle to put Epstein head onto the bed, window sill or other protrusion against which the assailant could then lodge Epstein's head and apply force to his body. Something which, yet again, would be precipitated by a struggle and would leave ample evidence of such on Epstein's body and in the cell.
But hey, I mean, it is not like suicidal people show great determination to kill themselves. It is after all trivially easy to jump in front of a speeding train, slash open your own arm or tie, secure and put a noose around your neck...
The two guards with access to the CCTV were slacking off and not doing their job. I wonder what reason they would have to erase the CCTV footage...