He acts as a bully - takes Greenland and then the EU doesn’t do much in the short term but long term the US economy suffers from broken alliances and isolationist policies.
Pretty much this but he knows it’s a back door method for getting out of NATO and also proving to Putin, Kim Jung, etc. that the alliance has no teeth since it didn’t act to protest Danish territory from being illegally annexed and invaded. I think Trump will at some point soon do a Gulf of America and just claim that it’s now US territory as a first provocative action. Then you’ll obviously see a heightened troop presence there. Then we’ll all be waiting to see what Danish troops or NATO does. Everyone assumes nothing because Trumps claim is illegal, not recognized, and the territory is currently unable to be colonized. So as soon as Trump dies or is kicked out of power the Danes will just assume it’ll eventually come back to them officially so it’s not worth going to war with America over. That being said the goal here as I first mentioned is destruction of NATO. Everything the guy does in the end points to helping Putin and promoting authoritarianism.
Then they take Incirlik in Turkey, Keflavik in Iceland, Diego Garcia in the Indian Ocean... Great ideas!