The guard’s supervisor would know who could be relied on to be unreliable. They would know who falsified logs and who slept on duty. Then, they worked them plenty of overtime and put the two bad guards on duty together. The scene is now set.
Either they knew Epstein was suicidal or they knew no one would notice if his cell was entered. One interview I read from an inmate who had served time there said, the sheets are two thin to support a man’s weight. Another interview from a doctor said that it was almost impossible to break the bones broken from a lean-forward type of hanging. Suffocation, yes. Broken bones, no.
On picking this particular prison either the ball was dropped or it was very carefully handed off.