i actually did the research into it. greenland has a good amount of rare earth minerals, and over 55 billion barrels of oil potentially pumpable that they refuse to tap because of 'environmental' concerns. greenland is unironically dinojuice central in the northwest of the planet, and we are exactly the right nation to mine that lithium, copper, drill that oil! i also noticed that denmark, despite being so insistent that they don't own greenland and that it's always greenland's choice, has been making statements about 'territory of the kingdom of denmark' an awful lot for anti-imperial eurofags, which really put a damper on the idea that denmark doesn't care if they lose greenland.
i think they know it would make them even smaller than they already appear on a map because now they lose the coloration of greenland too. i also pointed out that in day to day life, greenlandics wouldn't see any change at all, other than being far more able to complain about their own government than they are under any european power.