Musk expected substantially more work out of his employees for the same pay. Of course many employees would leave.
It has been barely a month since Musk acquired Twitter. That is not nearly enough time to sort out personnel issues/pay. I retired as a salaried employee. Being on salary means you have to put in extra hours when the core business requires it. I've been in a few toxic work environments over my working career. Who quits only after a month with a new boss?