That's why he wants Greenland.
This might by why someone within his regime wants Greenland, but Trump?... No. I don't think any reasoned conclusion matters in convincing Trump. It is entirely more likely Trump was convinced by things like "no other president could do it", "we can name it Trumpland" or "it's center is filled with cream".
I have always wanted to ask an ICE agent if they find it tiresome having to tuck their clown nose into their mask every day.