Even Kim Jong Un is not as stupid to know very well that if they launch first, the US and its allies will wipe their ass off the earth.
So far NK had no reason at all to launch first, because they have nothing to win and all to lose as long as the US are "just there" without actually doing anything unless they get hit just like Pearl Harbor.
Things change dramatically with a psycopath at the White House who at any moment could attack first. If the US does so, NK will certainly get wiped off sooner or later, although the guerrila warfare given by its brainwashed citizens could get worse than Vietnam. But on NK leadership eyes, if they're going to be attacked anyway they have no reason to restrain themselves: as they'll eventually lose all, any damage they could deliver with their payloads will be essentially free.
I'm not supporting NK's dictatorship, but that's definitely not the way to deal with.