It depends. I think it's totally possible to be friends with someone for decades and not know that they were secretly a rapist. It's not like rapists go around telling everyone about their crimes.
However, Epstein was extremely well known for pimping out children to rich pedos. Anyone who was friends with him more than likely knew. Plus Trump made that infamous quote about how Epstein likes them on the younger side. Trump also went to Epstein's island several times.
So in this specific case, it doesn't look good.