Could have been a case of other people not seeing the rape because they were so accustomed to men being pushy and coercive that it looked like "Oh, hey, she's having a fight with her boyfriend", or ... whatever, no idea.
Putting the onus on men to prevent other men from raping when they see it happen would be a first step in the right direction.
I would have thought that went without saying, but apparently it doesn't.
(I found it very telling that in this one case where an American man raped an unconscious girl and even photographed her, it was two Swedish men who noticed and stopped him. Could be coincidence, but could also be Americans considering this so normal they didn't even notice)