Hillary understands international relations policy and Trump understands how to profit from international beauty pageants, or did, until he screwed up recently by attacking Latin Americans. Hillary's appeal is to the rational, thinking mind, while Trumps is to the irrational illogic of Us vs. Them.
"Make America Great Again" is not a policy, it is only a stupid slogan.
When, precisely, was America greater than now?
This country has been at war of some sort or another since 1941. There was WWII, followed by support against the partisans in Greece, then the Korean War, with interventions in Guatemala and the Dominican Republic, then Vietnam, Lebanon, Grenada, Panama, Iraq I, Bosnia and Afghanistan and Iraq II.
The US is still great, but in a changing assortment of areas. The slogan is only an appeal to the emotions.