If an assistant is directly insubordinate then that assistants time on that job is numbered. And rightfully so. Your boss asks you to do something and you don’t because you think you know best then why are you working for that person in the first place. Or if you can’t take your boss constructively criticizing you when you mess up then your time as an assistant for said HC is numbered. A HC should ask you to do something one time and you do it with a sense of pride.
I’ve also seen the “look at me” assistants not last long too. You know the ones. Always at the meet networking for the next job. Assistants without loyalty need to move on