So in rethinking DT's administration's "policy" on NK I think it's possible they might be playing them exactly right.
Basically alternately threatening them while also playing to Kim Jong Un's vanity and running this "You know he's a pretty smart guy, probably does really want the best for his people but is just a little misguided, we should do lunch sometime and talk it out" routine.
Seems essentially like the "Silver or Lead" option that the South American cartels have operated by. Give them the opportunity to feel like a big deal, bluster a lot, and then offer a face-saving option that lets them bow out while looking like the victor (to their own people at least) while actually providing concessions/guarantees in some kind of deal behind-the-scenes.
"Yeah, we talked it over. North Korea seems pretty smart and tough, yep yep. Wouldn't really want to mess with them I guess. Glad we could come to an understanding."
Kim Jong Un might be thinking "Oh, here's an American who understands me."