So blaming rape victims is never a good start, but here we go.
These were very young men in high pressure enviroment. Teenagers, mostly. Maybe 18/19, but not mature adults. They had no support network, as even the coaches turned a blind eye to it as you can see with Jim jordan who they reached out to get help from. This happened basically as the Internet was first starting, in the 80s/90s, so no social media to reach out to.
The “doctor” used sport exams as cover for his sexual assaults. These young men thought it was just them not “being tough” about part of their sport. They didn’t know he did this to a hundred other men.
They probally did know, that even if they did come forward, victim blaming assholes would say it was their fault for not “kicking his ass.” That they would be shamed for being weak about not only being raped, but by not “being manly” about it.
So yeah, like most sexual assualt, the rapist targeted young, vulnerable people unsure of themselves who he knew had no support network. Then, like now, he knew people would blame them as much as possible, and people continue to help rapists by doing so.