There’s not be a single reason. In a few jobs when I was younger, it was usually the manager nobody liked, the one that let you know they weren’t there to make friends… they were usually the likely ones. A girlfriends parents (again when I was younger) was split. Her Dad for a good while refused, but eventually came around. He clearly didn’t like me (I think it was just an over-protective father sort of thing). More recent was someone who just had a superiority complex at work. I can only speculate as to what was wrong with this person or their motive, but they were the one that stopped “mid-name” to switch.