It's because a lot of the men at the top of these institutions either think that women are exaggerating, lying, being 'hysterical' - and even if they're not, the men in charge don't see the offence as something worth ruining the poor little sex offender's life over.
See also the Brock Turner case in the US, or, to a lesser extent, more recently the Daniel MacFarlane case in Scotland - his victim had recordings of him admitting that he raped her, there were messages submitted as evidence where he admitted it, and he still was allowed into Edinburgh University whilst on trial for rape, the verdict wasn't unanimous, and he received a shorter sentence due to his age (late teens when he raped her, but was 23 when he was still denying it and forcing his victim through horrendous cross-examination, and absolutely no remorse). He got five years, but it's so depressing when you're just glad a rapist has ended up in jail at all, instead of either getting with it, or just getting a slap on the wrist.