Ok chaps, allow me to suggest a somewhat optimistic take
Epstein knew that him dying would, as has been pointed out earlier in the thread, ensure that there will be absolutely zero legal challenge on searching his other properties and getting all kinds of dirt on all kinds of people. People who had utterly failed to bail him out and had infact likely been trying to plea bargain their way out of serious consequences by testifying against him.
He also likely knew that his suspicious suicide in jail would ensure an absolute clusterfuck of attention and outrage be thrown at the case for god knows how long afterwards.
He was also almost certain that there would be zero fun way out of this for him, and he had either a nightmarish prison stay ahead of him or just straight up execution.
What if this really was an honest to god suicide? What if this was his final and ultimate "fuck you" to everyone, those who wanted to try him, those who failed to defend him, and those who were trying to snitch on him to reduce their own punishments?
This could well have been his ultimate Scorched Earth policy to ensure if he went down, everyone else went down with him