That's the main reason. And it's a new shiny thing to distract from all the campaign promises he never intended to actually deliver. Yes Greenland has future potential for mining and oil but it's people don't want that and besides it's really not even economically viable right now due to its remoteness and arctic climate

1. He thinks himself a conqueror/royal.
2. It's a distraction from the legal shitstorm he's about to face.

4. Distraction from the coming avalanche of Executive Orders.

5. Distraction from his Fucked-up-Four nominees (Gabbard, RFinKjr, {C,K}ash, Hogsucker).

6. Distraction from his demotion to Vice President elect (co-president, if you insist).

financially on Greenland.

He's got a way to make money off of Greenland.

That's all he really cares about.

Trump's big ego and foolishness are on display. He probably thinks he is more than doubling the land mass of the US, when Greenland is about a quarter of the size, still even a 25% expansion would inflate his ego.

One - it would pit nato allies against eachother which serves putrid putin well and two - that military base in Greenland protects Europe from russia so of course depraved donnie and putrid putin want it in donnie's hands.