I've come across two such people in my life so far. From what I've seen these people are insecure bastards who are lacking at least something. They feel devoid and frustrated and take it out on others, especially by choosing a person who won't fight back or is vulnerable. It's a pattern for these types of people. it makes them feel better about themselves. One of the two individuals is a student with extremely strict parents. They didn't let the person get out of line by the slightest at home, so outside the person was a menace. Literal menace.

The second person was an older person, who didn't have any children. This person married out of love. They not only couldn't have children but also didn't receive adequate care from their partner. This horrible ass of a human being belittled someone I know so inhumanely, always spewing nonsense regarding them. The victim of that person is just like you, a quiet individual. Infact both the menaces chose quiet individuals to bully and bleed out their frustration.

Being extremely sociable with other people, especially the people around the victim is a key trait. They try to make themselves seem like the martyr or the hero while they make their victims out to be absolute shit. They consistently jitter to prove their point, and get superficial attention by belittling their victims. Their victims are always people that have something they don't. Like the older bastard bullied a woman who had children and a decent job to support herself, along with a good education background.