Trump has publicly talked about buying Greenland since his first term. This is an article from 2019:
https://www.theguardian.com/world/2019/aug/18/trump-consider...
https://www.theguardian.com/world/2019/aug/18/trump-consider...
Yes, it hasn’t been brought up during the last four years because he wasn’t president. Now that he’ll be president again it’s suddenly relevant.