Why do people put in the effort to be assholes?

My mother and husband are both the sort who would always choose to make someone feel bad rather than good. Happiness is not something they feel easily or often. Vulnerability is scary to them, and being kind is, in a way, a vulnerability. I think that’s how they processed their growing pains when they were young. Do unto others before they do unto you. I’m sure there are as many reasons and lack of reasons as there are cruel people, but that is one perspective. The presence of cruelty teaches us compassion, holds up a mirror and gives us a choice. I think we can thank our lucky stars when it doesn’t make sense to us.