I would guess a person's life circumstances. Humans tend to reflect pain they're experiencing onto others. If you're hungry, that's a form of pain. If you're neglected, that's a form of pain. Even the sons of billionaires experience pain, probably in a way that's hard for reg folks to grasp.

Also, I think your dopamine regulation being all messed up might also contribute. Those people who seem to flail and rage because nothing can seem to satisfy them.

Also, everyone does terrible things and hurts others. You can be charitable and kind from one perspective and an oppressor in ways you won't allow yourself to see. We all do it.