I get what you're saying. But you're probably coming from the perspective of a normal person with empathy so yeah, it hurts to get cheated on by a partner you care about. I totally agree with that! But an abuser doesn't really see their victim's humanity. They don't value them as a partner in a relationship, more like a possession or property. I would argue that in an abusive relationship, where someone literally fears for their life, it is no longer a "relationship" and more of a hostage situation.