But successful deterrence requires credibility
You might want to add “Stability” as well. Kim is only crazy because he comes from a long line of crazy and thinks his behavior is normal. Plus, no one will dare tell him his behavior is anything but normal. To Kim this war of words is the status quo that keeps him in power. It has worked for the two generations before.
Trump on the other hand is a moody unpredictable, disinterested bully who is out of his element. If he had the slightest idea of foreign affairs he would have known that hearing bluster from the DPRK is just standard nonsense every president deals with. It is not a challenge to go out and brawl in a parking lot behind a bar. Yet, that is how Trump reacted. Like an unstable insecure maniac.
So the war of words may be bluff on one side (Kim) but it is all adrenaline and mental issues on the other side (Trump). Not a good mix.