I think the Sparrow was a big let down. He seemed so clueless and ineffectual it seems out of character for him to drop the ball so brazenly.
It was the same arrogance that Ramsay Bolton displayed. Sparrow bundled it with false humility. When you always assume that you're the smartest person in the room you limit your ability to learn and react. Though Bolton was sitting very pretty until the Knights of the vale showed up.