Why have so many White House aides been ousted?

I think it was clear at the time of Trump’s infamous Charlottesville response presser meltdown that Kelly was in this to protect the institution of the presidency. I think that’s why McMaster, Mattis, Tillerson, and Cohn continue to serve as well. I admit that I labeled them enablers, and to some extent that charge sticks, but I am beginning to feel I might have been unfair in that assessment. They could be more like hostage negotiators trying to say whatever they can to keep this loon from driving the bus over the cliff.