Trumps domestic policy makes some sense. His foreign policy only makes sense in terms of isolationism. A typical American who understands nothing about the outside world.
His isolationism agrees with Socio Economic theory where isolationism means an economic recession.
In recession times the mood is down, no willingness to relate to other countries, protectionism at home.
There are many other current examples of this policy around the world.... UK! Catalonia in Spain. Italy. California.
https://www.rt.com/news/466935-trump-greenland-denmark-meeting/