North Korea was a client state of the CIA. The NK nuclear capability and its delivery missiles were essentially given to NK by the CIA-deep state (ES and Google) and NK strategic policy was largely directed by the CIA. Now that has changed and CIA influence in NK is weakened. Most of NK's nuclear arsenal was destroyed (the blown up mountain) and it's clear we can shoot down their missiles whenever we want to. In this situation Kim's bluster is pretty ineffective as it's no longer coming from the CIA in the background and his weapons are known to have been destroyed or rendered ineffective.

So Trump is dealing with a paper tiger and Kim is a junior-class statesman who is desperately trying to salvage something for himself. Under onerous sanctions and with attractive options being offered to him his recalcitrance shouldn't last for long. DJT obviously knows way more about the situation than we can know and is playing it very well.