In my opinion, I think Benjamin, the donkey, was most responsible for the "failure of the revolution." He was old, but he was experienced and educated. He could have given his talents to the workers of the farm and taught them what was really going on with the Pigs and all of the injustices that they suffered. He's a symbol of one of the major themes that I truly believe in, and that is if we don't get involved in some way, we are responsible for the problems which occur. So many countries just turned their heads when Hitler marched into other countries! If we allow bad behavior to continue without saying anything, or at least helping in some way, we are indirectly at fault. The link below takes you to a paragraph about the donkey and suggests that Orwell himself is personified in the character. I don't know about that, though. It seems surprising to me that Orwell, the master of political understanding, would be considered one who wasn't politically active. I would argue that his novels 1984 and Animal Farm helped to get his voice out into the world to teach others about each citizen's duty to his/her community.