SEOUL – When President Donald Trump walked out of his first summit with North Korean leader Kim Jong Un in Singapore in June 2018, his confidence was sky high. Trump claimed he knew “for a fact” that Kim would go home to start a process that “will make a lot of people very happy and very safe.” Since then, North Korea has carried out more than a dozen missile and rocket tests, says denuclearization is no longer on the negotiating table, has called Trump an erratic “dotard” and has threatened to deliver an unwelcome “Christmas gift.” Many lay blame on the North Korean regime, arguing it was never serious about dismantling its nuclear arsenal and presented an unrealistic set of demands when Trump met Kim for a second time in Hanoi in February. But there’s also plenty of evidence that Trump and his team bear responsibility, too, for derailing the negotiations – delivering mixed messages, failing to understand their counterparts, demanding too much and making undeliverable promises. So what went wrong? Trump persuaded China and Russia to impose some of the strongest sanctions ever imposed on North Korea. But even more importantly, according to Andrei Lankov, a professor at Kookmin…