Critics have argued that in placing such emphasis on his personal dealings with Kim, Trump has undercut his advisers. After the second summit ended without a deal, however, the Trump administration is pointing to a silver lining: The summit’s collapse could paradoxically empower the leaders’ diplomats and technocrats.

Ahead of their meeting in Hanoi, “it just seemed pretty clear to [Biegun] that Kim was playing the waiting game for the one-on-one” with Trump, the Connecticut Democrat Chris Murphy told me. Biegun’s argument is that walking away “sets the conditions for serious negotiations [by lower-level officials] that couldn’t happen until Kim realized he couldn’t pull one over on Trump.”

Asked for comment on these and other characterizations of Biegun’s briefing provided to The Atlantic by senators who met with him, a State Department spokesperson declined to “comment on remarks made in a classified setting.”

Read: Trump thinks he’s the only one who can fix North Korea

At a conference in Washington, D.C., on Monday, Biegun defended Trump’s approach of engaging directly with Kim. “We have tried for 25 years to percolate positions up from the working level to the leadership level, with no success,” he said. Kim is the only “one who can truly create the space for my counterparts sitting across the table from me to be flexible, to be agile, to be creative, to find solutions to these issues.”

Nevertheless, a senior State Department official conceded that Kim has yet to grant his subordinates space to negotiate. “We need the North Korean negotiators to have much more latitude than they did in the run-up to the summit on denuclearization,” the official said in a briefing with reporters last week, while stressing that Trump’s meetings with Kim were an indispensable feature rather than a bug in that effort.

Ron Johnson, a Republican from Wisconsin who also attended Biegun’s briefing, told me he still understands the leader-to-leader talks to be a critical component of the administration’s approach.

As Johnson sees it, Kim wrongly assumed that he could wring economic concessions from Trump for little in return, as North Korea’s leaders have done with previous American presidents. “Obviously, he came [to Vietnam] thinking he could talk Trump into a bad deal, and good thing he wasn’t able to,” the senator said.

But Murphy left Biegun’s briefing with the sense that both leaders—in spending the months following their first summit in Singapore pinning progress exclusively on their personal abilities to make a deal with each other—had made strategic mistakes ahead of Hanoi.

Kim’s was his “refusal to engage in any serious pre-negotiations” through his subordinates, Murphy told me. “Biegun was knocking at the door, day after day, and for the most part, nobody was answering. Kim seemed to make the calculation that he had buttered Trump up so sufficiently to be more likely to get what he wanted from Trump directly than through intermediaries.”