What I do not understand is why Jon did not try to negotiate with the knowledge about his parentage. He could have told Dany that he will help her win the Throne and keep silent about his parentage but that she should leave the North be in exchange.
Jon rejects the Throne, she gives independence. That would have been a good deal.
Is Jon so trapped that he lost his negotiatiating skills? Does he suspect that Dany would not be satisfied with this? Does he suspect that she would not keep her word?
Why does he not try to plan for the future? I guess he thinks he has to stick to his promise, but why does he not try? Does he think it would be futile to try to reason with D anyway? I really like to know what goes through his head. Anybody an idea?
In a way it is a typical set up for a drama. If the person involved would be prepared to let go of their goals, the tragic outcome could be prevented. But for external reasons Dany cannot let go of the Throne and also for character reasons.