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.
I added this to my reading list this morning. It's 61 pages of RAND - which tends to be a little dry - but the basic argument seems to be that we could fold North Korea down so long as we took care of the nomenklatura and made sure they had: 1) safety from reprisal by the proletariat 2) secure socioeconomic position in any new regime 3) improvement of the lot of their nation Basically, if we can make it better for the country without fucking over the intelligentsia we could probably get away with it. They use the reunification of Germany as their exemplar and the collapse of Baathist Iraq as their reason not to try otherwise. I think North Korea is pursuing a nuclear weapons and missile program because it's the quickest way they have to the Big Boy Club. They're basically looking for the pain point where we're willing to give 'em amnesty for six decades of fuckery.