I only very recently found out that Trump expressed an interest in 2019 and was even more surprised to learn President Truman offered a $100 million for Greenland in 1947.
Lurking behind all this is the fact that Russia and China are making inroads into the Artic which security wise would be bad news for America. The base they already have there is an early warning set up and it's looking like enlarging that and setting up a deterrent is needed.
Trumps noise has already stirred Denmark into increasing defence expenditure on Greenland (I think they literally have something like 2 small boats and 12 dog sleds) and now we have NATO wanting to get involved.
As we've said before, Trump will make an outrageous suggestion/demand and slowly things will move in the direction he wants, it's the way he operates, it might not be to everybodys taste but he gets things done.
I read yesterday that BMW have started lobbying the German Govt to reduce tariffs on cars imported from America, I didn't know that yank cars to the EU attracted a 10% tariff whilst EU cars to America attract a 2.5% tariff. Suddenly some of his views started to make more sense.