What if we just offered to buy out their position? Pay them handsomely to step down with full immunity and protection in return for the entire control of NK?
I doubt that China would buy that agreement. (Although I suppose they could buy the DPRK).
Better a general in Hell than a corporal in Heaven.
I suspect that even if Daddy got you the job, managing to stay as leader of the DPRK probably means that you probably like being in charge, even of a basket case.
Sabre rattling is possibly a fun way of feeling important.