And with Hamish, he has the right mix of arrogant prick and self deprecating humor to gain an army's loyalty. While Tyrion is smart, arguing about legal rights instead of getting bogged down in being right or wrong, but not nearly as charismatic as Hamish. Which will be a problem for the Lannister's going forward. Wither they win or lose the court case, they aren't going to look good by the end of it.