Trump's strategy now with North Korea is to bring the hermit kingdom under the protective wing of the United States in the same way that we brought South Korea under our wing after the Korean war. This is why "security guarantees" became the main carrot stick offered to North Korea in exchange for denuclearization. This is similar to our arrangement with South Korea after the Korean War. The purpose of all of this is in trying to bring Kim under our wing and under the wing of South Korea we help drive a wedge in between his regime and the communist party of china's regime.
Both sides in this trade war understand one thing: The Korean peninsula will be united at some point in the not too distant future and the only question is what will it look like? China, led by the communist party wants a Korean peninsula in its image while South Korea and the U.S. want a united Korean peninsula in its image.
The trade war is an attempt by the Trump administration to end very unfair trade practices by China including the forcing of foreign companies to hand over technology secrets in exchange for market access, economic espionage by China and the theft of intellectual property but it is also about sending China a message that the U.S. is very serious about moving Beijing in the direction of international norms not only on trade but everything else including those of governance and territorial disputes as in the South China Sea, Taiwan, etc.