You need to study N Korean history and the N Korean mindset. This is something every N Korean expert, including defectors, will tell you. They are a regime that is very nostalgic for the Cold War era, when the Korean peninsula was at the center of global geopolitics. They desperately want to recapture a sense of that centrality and importance. A summit gives it to them. That's fine. But first you extract what you can from them. The summit is the reward once those concessions are extracted and banked.
That is their perception. It provides no tanagble benefit. It should not be something that is a roadblock to peace.