I've always thought that Kim got a taster of what a directed EMP can do to one's underground nuclear facilities. I don't believe that the EQ that caused tunnel collapse under mountain where NKs nuclear facilites were house was natural. Believe it was EMP induced on DJT's orders. DJT negotiates from a position of strength. Something made Kim roll over and I'm pretty sure it was a demo of what could follow, not just a threat.