Young men have a strong interest in sex and sexual matters
I wonder, though, if this was not so much about the sexual act but more about hatred, a weapon to use against women who had (unwittingly) annoyed them. Rape is, after all, used as a weapon of war.
At least one was also anti-Semitic and thought Hitler was a hero.
Two (at least) were members of the Student Union Exec - horrifying that they were probably 'leading lights' at the university, organising events etc and at the same time leading this nasty, vile secret life with others.
Their names are out there and this will follow them - the university may put it behind them but future employers may not.