I disagree. NK is rational -- they are just operating from a very different perspective and conditions than most other nations.
The government is terrified that they will be overthrown by the US. Given that the US has basically wanted regime change since the 1950s, and often takes steps that harm NK and its government, it is perfectly rational for them to fear the US.
They rarely go on the offensive; when they do, it's not as a pretext for a larger war. It's more to extort money out of SK, China and/or the US. For example, a few years ago they made demands for huge amounts of food and money to come to the table with SK. When their demands were not met, they sunk an SK naval vessel.
They are pursuing nuclear weapons for what should be an obvious purpose: To prevent an invasion by the US. The US would never have invaded Iraq or Afghanistan if they had nukes, and that's exactly the fate they want to avoid.
Meanwhile, their isolationism gives them significant control over the population; it keeps their enemies guessing; and the leaders still get all the consumer goods they want.
We see their government as irrational and unreliable and unpredictable... which is how their government sees the US. Even with relatively normal leaders like Bush 43 or Obama, there is no way for them to be sure the US won't turn them into a punching bag, in order to distract the American people from some other issue, or to "look tough," or because of a news article.
Ultimately, labeling NK as "crazy" makes it impossible to understand their motivations. I don't see how that's useful.
