If Musk truly fired Ms. Brown because his companies operated smoothly in her absence, then I think he was an idiot.

If the company falls apart when you go on vacation, that is the mark of a lousy employee.

A good, competent employee ensures that she has adequate back-up and ensures that all critical tasks are completed as much as possible before she goes on vacation.

Therefore, the anecdotal 'evidence' does not stack up, and I tend to agree that Musk concluded he needed a team to do the work that Brown was doing.

He may also have realized that Brown was tremendously overworked and that firing her would set her free. In addition, he may have realized that his extreme dependence upon her was harming him. What kind of executive has to be pulled out of meetings to attend to other duties? What kind of father has to have someone else schedule time for his children?

Musk needed to let Brown go as much as she needed for him to let her go, even if neither of them realized it at the time. I suspect both of them did come to realize it later.

I don't think Musk was an ungrateful bastard; I think he got a wake-up call and was smart. He realized that he was overworking his assistant and knew that neither of them would change their ways if he kept her on.