What is the mentality of people who spray everyone online? Jealousy, inferiority or mental illness?

Maybe it's a psychological problem. I can't see others' good and happiness. Always trying to throw cold water on others. I think it's fun to imagine others unhappy. In fact, they are strangers, they will never know each other, and they don't know why they are so malicious to others. Most likely, the real life of the network sprayer is like this, but we are lucky not to know Ta people in real life.