My Buffalo, Trump is not making these decisions. The man can't even make it through the day without needing to be shepherded around by secret service. He is presiding over a very complex, sprawling, coordinated system of government and he is responsible for communicating and selling decisions that 99% of the time are made long before they get to him. Nowhere would this be more obvious than with military decisions, particularly involving Russia. The US never dismantled it's ColdWar-era intelligence, planning, decision-making, contingency, and logistics apparati for dealing specifically with Russia. At no point has Trump ever studied military strategy, at no point has he ever been capable of understanding the strategic consequences of any decision involving proxy wars, encirclement strategies, great power conflict, etc. Anyone who actually believes Trump just came up with the desire for Greenland on his own is falling for the kayfabe. His job is to sell the decisions that get made by the joint chiefs and the CIA. That's it. How he sells it has to do with his psychology, but what he has to sell is well outside of his control, much like his bowels and bladder.