It made no sense. All the characters took totally random decisions, and this episode truly betrayed the most valuable quality of GoT: consistency of decision making and realistic psychology. One can accept flying dragons, but shallow psychology justified by the need of a spectacular entry (the knights of the Vale, after Sansa for not reason whatsoever did not mention this to Jon) really brings down the quality of this season. The writing is very bad, definitely contrasting with the depth of previous seasons. Many speculated that this is because the producers deviated from GRR Martin's book deeply. For example, since Sansa was not anymore with Littlefinger as in the books they had to devise this non-sensical trick of her not telling anything to Jon Snow to justify the last-second entry of the savior army. I honestly think this was the worse episode in GoT, as the big budget and spectacular scenes - truly spectacular admittedly - cannot compensate for the cheap story-telling. If possible, they make it even more obvious, as they highlight the change in priorities of the producers.