In polite society the idea of mature adults having sex with minors is generally considered so outrageous that it's easy to imagine how those around Epstein wouldn't have had to try very hard to convince themselves that the young looking girls around Jeff are totally adults.
It simply wasn't obvious to onlookers that Epstein was doing what he was doing, you wouldn't jump to assume that the young women around him were underage. Most of them apparently weren't.
Had Epstein surrounded himself with prepubescent children instead, it'd be far easier to assume that the people hanging out with him were interested in specifically minors rather than conventionally beautiful young women.