This is huge
"The hermit country's latest nuclear test, conducted in September 2017 at Punggye-ri, was at least 17 times more powerful than the bomb that was dropped on Hiroshima in 1945, according to The Washington Post."
I think it has more to do with the Olympics, the sanctions, and Trumps relationships with China, Japan and South Korea. Kim saw all of the money coming into South Korea from the world during the Olympics and wanted to be a part of that. The sanctions are crippling an already broken economy, and Trump has great relationships with the other economies in the area. AND Trump is not afraid to drop bombs on Kim.