Why do some people like putting others down?

Maybe it’s because I’m a highly empathetic person, but I feel bad if I even make video game characters sad or upset (I wish I was kidding 😅🤣), while there are other people who constantly, and I mean constantly put others down… in both real life and online. I got bullied for the mass majority of my school life and I’ve gotten vile messages and comments online. I just don’t get it.