I hate to put out speculation, but this a known speculation place.
NK obviously hit a snag that was not expected. We can see that Q or Qteam had devices setup to be able to drop during the meeting.
China trade deal not being complete, it's obvious that Xi wants to keep that bargaining chip until the trade deal is complete.
NK will happen, but after the China trade deal get's resolved.
Now a 3D chess player, that knew they had a deal, would get the media headed in the wrong direction, and make them have to flip.