I'm just speculating here but the Greenland expansion was likely in the works for a while but once Trump heard about it, he ham fists the entire diplomatic process by threatening force. Maybe the process was going too slow for his liking or maybe he was just high on the fumes of burning boats in the Caribbean but regardless, he harmed national security and the defensive posture of NATO because he's too dumb to just follow established procedures.

Remind me again, why do we need a toddler in the white house?