Many people have the assumption that to be a good leader or manager requires them to be a jerk. Being abrasive, rude, and snide with people are requirements they envision as being true and legitimate strengths. They feel if they aren’t a person who demoralizes other people with bullying tactics then they will be viewed as a push over and weak.
People like this feel they will be respected more if they rule with an iron fist. Often you will witness them being brash and demeaning to their subordinates. They think to be the tallest building in town requires them to tear down all other competing buildings with any height. This mentality is engrained early on in their career thinking this is the only way it has to be. They know it feels wrong but do it anyway. Being a jerk is actually a weakness. This is an insecurity that shows through their faux exterior.