So I saw a pretty believable breakdown that would absolutely explain this. It’s basically because they had a messy falling out over Trump being a spoiled brat. The timeline is as follows.

The inciting incident was Epstein putting in what he thought was a winning bid on a new mansion. Confident in his bid he then showed the property off to his good buddy Trump and asked some advice on some renovations he was planning. Trump then went to his Russian buddies, got a “loan” and put in a higher bid on the property ultimately winning it. This pissed Epstein off who was further confused because he knew Trump had been having financial problems and didn’t have enough money to cover the bid he put in. Six months later Trump sold the property to the same Russian who had given him the money in the first place for twice what Trump paid for it laundering millions of dollars in the process. Epstein correctly realized that Trump just used his property that he swiped from him to launder Russian money which pissed him off even more. Enraged he called Trump and threatened to expose the money laundering. In retaliation Trump then informed the FBI about what Epstein had been up to on his island which is what ultimately led to his arrest. Whether Trump and/or the Russians then silenced Epstein and whether that was about Trumps participation in Epstein’s crimes or about the money laundering who knows, but it definitely makes some pieces fit.

Edit: Dug up the video the claim was made in: https://www.youtube.com/watch?v=JTz6X5Bh_lw