Trump did not make a "sincere" effort for peace in North Korea. The idiot got pwned by North Korea by signing an "agreement" which said things that Trump didn't understand and were outside the bounds of US foreign policy position. In theory, Trump tried to glamor Kim Jong Un into a peace deal, creating a ridiculous propaganda video showing Kim Jong Un just how great peace would be. Trump put no more effort into North Korea than he did in ordering lunch. He didn't prepare, he didn't understand the situation, he just thought that he could Art of the Deal against people who he had no idea were much better at such things than he was.
You give Trump more credit than he deserves. George Conway is right when he says Trump does no strategic thinking and instead acts just like an impulsive six year-old.
He's a wannabe dictator who's attracted to brutal dictators if they're successful: He'd like to emulate them. That's why he's infatuated with North Korea's Kim, the Saudi Crown Prince MBS, and other dictators. Recall that he's an Adolf Hitler fan.
Trump is especially infatuated with Vladimir Putin, head of a major multi-country crime network. Not only does Trump envy Putin his power and virility, he is grateful for the many millions Putin-influenced banks and other firms have donated to keep the Trump real estate empire solvent. (With all the litigation and disclosures, is it known how many millions Russian banks have contributed to Trump?)
(Putin most probably also serviced Trump with some of Russia's most luscious call-girls, but this may have just embarrassed the Malignant Orange Narcissist. These days his libido is best satisfied by the inane skits he performs at his campaign rallies.)