I suspect that neither man really wanted the meeting. Kim was never going to give up his nuclear or missile program. Trump was only ever looking for that kind of concession. So Kim used the long-scheduled joint military exercises to suggest that he would cancel the meeting, and Trump used Kim's tantrum over that as an excuse to cancel the meeting. At this point, Kim has lost three hostages, but he has managed to soften his isolation and weaken the international sanctions against him. He got a lot of good press from Olympics and the junket to South Korea. He can now claim that he wasn't the one at fault for the breakup. He and Xi Jinping have restored friendly relations for now. Trump ends up with egg on his face, but he can now concentrate on backing out of his claim that he wanted to sit down with Mueller for an interview.