The reason that Trump is constantly unleashing attacks on others, and strange thoughts (like purchasing Greenland and windmills causing cancer) is simple. That is ALL that he has. He is simply intellectually and emotionally incapable of the coherent thought and hard work required to come up with any constructive policy.
The only good thing about that is that people -- including some of his base -- are now realizing that.
well, the US bought alaska, which worked out pretty well. maybe buying greenland is not so crazy after all.
This is over a century later and no one wants to sell Greenland.