There's lots of traveling involved going to meets plus they are together a lot. There's also a power dynamic where the coach is highly respected and there's a line of athletes waiting to use their services and if you don't do everything they say then you'll be replaced.

Plus there's a lot of grooming involved and they start slowly to make it seem normal and then cross boundaries. At that point the athlete assumes that if they complain that they won't be taken seriously and it will be the end of their careers.

It's similar with modeling. It might start with modeling jeans. Then they are told they can make more money modeling swim suits. Then underwear. Then model these panties but cover your breasts with your arms. Now just your hands, and it devolves from there. Then once they have topless pictures they threaten revenge porn and they are trapped.