Adam already laid it out for you in easy to understand english:
Originally posted by Adam_PoE
World leaders do not respect Trump. They do, however, respect the office of the President of the United States. And the leader of the most powerful country in the world agreeing to meet with a dictator gives his rule legitimacy, even if they are both total buffoons.
This has been the warming for decades regarding NK, it's not just a "der Leftist!" thing.