In short, Epstein may have been preparing to blow the whistle on Trump’s money laundering for the Russian mob. Trump got wind of this and tipped off the FBI about Epstein.

Epstein was trying to buy a South Florida estate. He brought Trump along to see it one time. A short time later Epstein found out that Trump had gone behind his back and placed a higher and ultimately successful bid on the property. He’d snatched it out from under him with a much higher bid. The problem was that Trump’s entire empire in 2004 was teetering on the edge of bankruptcy. It made no sense where Trump was coming up with $41 million to buy this property. Epstein suspected that Trump was acting as a front for a Russian oligarch as a money-laundering scheme. And in fact Trump did purchase and flip the estate two years later to a Russian oligarch named Dmitry Rybolovlev for $95 million, or a profit over $50 million dollars.

Epstein was pissed for his own reasons (he wanted the estate). But he also suspected the money laundering scheme. So he threatened Trump that he would bring the whole thing out into the open through a series of lawsuits. Right about this same time authorities got a tip about Epstein’s activities which started the investigation that eventually led to his eventual 2008 plea deal.