The simple fact of Trump's presidency is now this: All rails have been removed from the proverbial road. The men( and women) expected to mediate and mitigate some of Trump's wilder ideas and statements are now, nearly to a person, go — driven off by a President whose vision of the country and the world is both highly erratic and deeply held. And nearly to a person, those advisers have been replaced by others who have risen up in Trump's reckoning by telling him what he wants to hear.
Mattis' departure is the death knell of the idea that Trump could –and possibly would — adhere to any sort of “normal” order during his term as President. This is a President who has driven away the very people who he( and the country) trusted with steer him as a political leader in these difficult. Now there is only Trump — and those willing to enable him.