There's a theory I heard somewhere recently that part of the reason Trump is so interested in Greenland is due to his lack of understanding of maps.

The Mercator projection (which is how most 2D maps are displayed) makes Greenland appear to be the size of North America. It's large, to be sure (around 25% bigger than Alaska), but it's certainly not continent sized.

Obviously thats no justification for his actions, but found the explanation at least a bit amusing given his other odd misunderstandings (eg thinking people seeking asylum are from an insane asylum, thinking wind mills somehow affect whales, etc. The list goes on and on...)