they're all thinking about whose life they're going to try to ruin tomorrow.
The entitlement these people feel blinds them to reason and somehow in their brains what others would let go of and move on from becomes a cause for them to champion. That self-feeds and before too long they're stuck in a cycle they don't have the emotional and mental capacity to escape; each time they act out their little fantasy they gain a little more "power" for lack of a better word and it causes them to become a little more delusional each time.
Looking into history we can see these behaviours replicated in all sorts of people from the lowliest to the mightiest. It's usually the mightiest who do the most damage (I'm sure you can think of many examples) but the lowliest cause damage also. At the end of it all though, the victims can choose otherwise, take the tormentor's power away by moving on an ignoring the person...The person themselves though...they're stuck with themselves and have to, suck it!