The thing is that no-one had to do anything terribly wrong for this tragedy to occur.
The woman is perfectly entitled to discuss her uncomfortable experience. She was also discussing it with an ex which suggests a very tangled closed in group, and that may have been cos they were close, or she may have felt she had to give an account to her ex and his friends.
The man himself clearly felt devastated he had done in his mind an unintentional but bad thing, we don't know what. Oxford colleges are very closed and he probably imagined his whole uni experience of being shunned and couldn't see the way out.
Being uncomfortable after sex, feeling coerced or whatever happened is devastating. Being accused of doing that, even if you did, is life changingly awful, and it's not something most young men would just get over, nor the woman.
So sad that none of them sought help from tutors or student support for this.
I have supported a student accused of something similar. In his case he was extremely fortunate that he was with others who were witnesses and there was Cctv cooborating his story, most sexual encounters are not of this nature! Why the person lied I have no idea, I can guess but have no proof. The police did, rightly, a very thorogh investigation. He told me he thought of suicide.