The American team’s lack of experience in negotiating with North Koreans, as well as a lack of preparation, may have contributed to the collapse of this week’s Hanoi summit between Kim Jong Un and President Donald Trump, who favors top-down diplomacy, according to experts.The two-day summit that began Wednesday ended when Trump walked out on Thursday without a denuclearization deal or a declaration of peace to end the Korean War, a move met with approval in Washington, even though the summit began with hope of concrete agreements on denuclearization.“Sometimes, you have to walk, and this was just one of those times,” Trump said at a press conference Thursday. The talks broke down because, according to Trump, North Korea demanded all sanctions imposed on the country be lifted in exchange for its offer to dismantle its Yongbyon nuclear facility. Later, at a separate press briefing in Hanoi, North Korean Foreign Minister Ri Yong Ho said North Korea had asked for partial sanctions relief in exchange for continuing to halt its nuclear and missile testing.The Hanoi summit was the leaders’ second, taking place eight months after their first summit in Singapore last June, which produced a widely criticized vague agreement. ‘Correct decision’Experts agree that Trump did the right thing.“I think sometimes the best deals are the ones you walk away from,” said Christopher Hill, a chief negotiator with North Korea during the George W. Bush administration.Joseph DeTrani, a former special envoy for nuclear talks with North Korea, said, “The president made the correct decision.”Robert Manning, a senior fellow at the Atlantic Council said, “Trump … deserves credit for that moment of realism.” But according to experts, the summit collapsed in part because Trump’s top-down style left little room for U.S. negotiators to reach agreements during working-level meetings with their North Korean counterparts who have much more experience in denuclearization talks.Sung-yoon Lee, a professor of Korean studies at the Fletcher School of Law and Diplomacy of Tufts University, emphasized that North Korea’s “chief full-time America-handlers” average three decades of on-the-job experience, while the current U.S. negotiators have logged about 2½ years of dealing with North Korea.“Who has the advantage?” Lee asked. Many of the State Department’s most experienced North Korea experts have retired recently from government.The final agreement on denuclearization was left for the two leaders, who failed because “both Trump and Kim overestimated their respective ability to take the other side into a deal they wanted,” Manning said. ‘Top-down approach to negotiating’“This was the risk you take when you do a top-down approach to negotiating,” said Dennis Wilder, the National Security Council’s senior director for East Asia affairs during the George W. Bush administration. “In other words, clearly, an agreement hadn’t been made before the men got to Hanoi.”Wilder said Kim misjudged Trump and “overplayed his hand” and “overreached in the negotiations,” thinking that he could “get something big for putting very little on the table,” which was based on his previous experience in dealing with Trump, who was “quite easy on the North Korean leader and did not demand a great deal of him” at the first summit.“The failure of the Hanoi summit shows the downside of top-down diplomacy,” Manning said. “I would have insisted on having the basic framework and some minimal nuclear-for-benefit trade-off agreed to before I agreed to a summit.”Hill said, “I think it kind of speaks to some of the preparation, which I thought was inadequate.”He added, “There needs to be a clearer understanding about [reaching agreements prior to talks] before they ask the president, before the president gets involved.” WATCH: Failed Hanoi Summit Could Reset Productive Nuclear Talks Wilder said U.S. negotiators probably “knew perfectly well what North Korea’s position was,” but think Trump felt his chemistry with Kim would enable him to strike a deal that perhaps he thought Special Representative for North Korea Steve Biegun and lower-level North Korean negotiators “wouldn’t have [had] the latitude” to strike.“I think [the Trump administration] decided to somewhat gamble, to roll the dice to see what they could get,” Wilder said.Manning, of the Atlantic Council, thinks Biegun tried to make an agreement before the summit, but that the North Korean side probably refused because Kim wanted to deal directly with Trump at the summit.“Steve Biegun did make a major effort to learn from past Korea diplomacy, meeting with dozens of those previously involved in the diplomacy, and tried to build on the lessons,” Manning said. “But North Korea would not negotiate a minimal nuclear deal at that level because they thought Trump was a soft target.”Hill said, “To have it just fall apart” signifies that the diplomacy was not quite ready “to be brought out of the diplomatic oven, if you will.”‘Experience matters’In dealing with North Korea, Manning said, “Experience matters.”Wilder said, “On the North Korean side, you have people very, very, very expert in negotiating with the United States.” He continued, “They’ve spent their entire career doing this, whereas on the American side, they’re relatively less steeped in all of this.” According to Korean studies professor Lee, U.S. Secretary of State Mike Pompeo has two years of dealing with North Korea, and Biegun, has half a year and National Security Adviser John Bolton had five years of dealing with North Korea, including time in the George W. Bush administration. Former South Carolina Congressman Mick Mulvaney, Trump’s current acting White House chief of staff and director of the U.S. Office of Management and Budget, has little foreign experience. On the North Korean side, Minister of Foreign Affairs Ri has 35 years of dealing with the U.S., while Kim Yong Chol, head negotiator on nuclear talks, has dealt with the U.S. for 30 years. Vice Foreign Minister Choe Sun Hui has 25 years of experience with the U.S. And Kim Kye Gwan, a leading negotiator during the Six-Party talks who is also believed to be working behind the scenes advising current negotiators, has 30 years of experience with the U.S.Going forward, Wilder thinks Trump “is going to be “a little more wary” of having another summit with Kim “without some understanding beforehand.”He added, “So I would guess that he is now going to give Mr. Pompeo and Steve Biegun more authority to negotiate.”As for North Korea, Lee thinks “Kim was taken aback” and is likely to “regroup and dangle another sweet carrot to Trump.”Lee said Trump will most likely “take the bait and settle for only a partial freeze of Kim’s vast nuclear and missile programs while bomb-making goes on in other undisclosed locations.”“For Kim, two steps forward and one step back is still progress,” Lee said.