It is quite obvious what "triggered" Trump's tweet. It was the North Korean pullback from the liaison office. But Bloomberg, like other U.S. outlets, ignores that quite obvious explanation. This constant ignorance of the action of the other side is one of the systemic problems U.S. media have.

New sanctions were announced to which North Korea reacted negatively. Trump, who wants to keep the door open for future negotiations, took note and pulled back on the sanctions. But John Bolton intervened. The sanctions were kept. A well sounding but implausible explanation was found. North Korea accepted that and came back to the table.