It may not just be about the minerals....

It could be about leaving NATO.

US (Trump) feels they need Greenland for "security".

They currently have (almost complete) access to use Greenland via NATO and the existing agreements with Denmark. So there is no need to extend this.

However, if the US would want to leave NATO, they would no longer have access to Greenland under existing agreement.

Therefore, if the US wants to leave NATO and still use Greenland (both militarily and for resources), they need to acquire Greenland.

Acquiring Greenland would allow the US to control the entire western hemisphere, leave NATO, and abandon the eastern hemisphere entirely.