Why doesn't the hard conspiracy theory hold water for you? The motive is much more reasonable and prison assassinations are hardly some unheard of impossibility especially given the sheer amount of extremely powerful people with a reason to kill him.
When competing theories nessecarily have the prison guards who have been overwhelmingly successful in preventing suicide attempts and somewhat successful in stopping suicides after they get to attempts to hold the idiot ball it stretches credulity. Why haven't more prisoners been suicided if these guard were on such a hair trigger they would murder somebody at the expense of children's safety?
On the other hand compromising a prison guard and blackmailing him into murdering Epstein or else would be trivial for an Epstein associate. I just don't get how enraged prison guard is a remotely more plausible motive than prison guard being given a compelling reason to kill Epstein by an associate. It seems like setting out to prove the conclusion Epstein wasn't killed by the rich.