@futurebird I think it boils down to him wanting his face on Mount Rushmore. Taking Greenland has no practical benefit. He might be able to enrich some of his people but not worth the cost.

He was raised on a pathetically simple story about American history that lionized national expansion. He thinks if he can push the borders out he will finally be universally recognized as a Great Man.

Same with Putin, who wants to be Peter the Great.