So, I think Trump's appeal to him was perfect. The US has no interest in invading North Korea, or even overthrowing the government. We simply want a peaceful Korean peninsula.
And we didn't have to offer loads of money to move North Korea towards peace-we only had to offer something that we were already doing-not interfering.
It may be that Kim’s “rocket man” persona was a sort of outreach, acting like a bully til the big kid on the playground confronted him and told him to knock it off, but then invited him to join the big kid club. I don’t think anyone considers Kim to be stupid, he’s well aware of the western world and how NK is failing, but he needed a path to follow and Trump has given him one.