Case in point? India and Pakistan. There has not been an open shooting war there since they both went nuclear. India is pushing its space program for the same reason that the US and USSR did: take the satellite off the rocket, put a nuke on it and now you can project "Don't fuck with me" across half the globe. NK sees Trump as weak and distracted, my guess. The tests are to remind the world that they exist, and to drag the big powers to the table to extract concessions on food and fuel, like they have done for decades. As you have pointed out here previously, nobody wants North Korea. The South does not want to take the place over an integrate 25 million starving illiterate brainwashed peasants. China does not want to deal with them, and wants them so the US does not have bases on its border after the South takes over. So we get this rouge state that is allowed a limbo status because it existing is the better of the other options.