There's a limited suite of possibilities: 1) He suicided, despite the extraordinary measures at MCC to prevent that, and the fact that it has never been done at MCC before. This prison is extremely secure, and holds very competent criminals, like El Chapo, terrorists, etc. I consider this the least likely possibility. 2) He was assassinated. Given the report prior to the announcement of his death that he had been moved in the wee hours to a single cell by someone claiming to be an employee, that guards were moved from the area, that the camera failed, and the extremity of the danger to politically and financially powerful parties of the testimony that would certainly emerge from his trial, it's hard to discount this option. Seems the likeliest possibility to me. 3) He escaped. Without other comment, I don't buy this. El Chapo didn't, the terrorists don't, I don't think Epstein did. 4) Witness protection. Possible, but given the danger to the international order of the testimony and the undeniable lack of political will to prosecute royalty, heads of state, and other powerful individuals he was likely to be blackmailing, I have little confidence in this. Given the international political upheaval that prosecuting folks like Prince Andrew for raping children would necessitate, Trump's DOJ is probably far more likely to have killed Epstein themselves just to end the problem his testimony would engender politically, and this is ignoring Trump's tutelage by Roy Cohn and current possession of the voluminous evidence used by Epstein to blackmail the rich and powerful.

I doubt Epstein's trial was politically possible. Whether he disappeared or was killed, I expect every effort will be undertaken by the enemedia to avoid international political fallout from the evidence already revealed, and to keep any more revelations impossible. I suspect Nick Tartaglione and Ghislaine Maxwell have pretty short life expectancies due to their exposure.