All of the pigs, including Squealer and Napoleon, have expert knowledge. They are literate and they know what is really going on at the farm. They have enough knowledge to be able to inference that Jones will be coming back. The pigs also use propaganda to get the animals against Snowball.
After the revolution, the animals have total control of Animal Farm. Each of the animals have an equal voice. They elect the pigs as their leaders because they know that the pigs are the smartest. Eventually the pigs begin to gain more power and stray farther away from the idea of democracy.
In the beginning, Jones is a single ruler who has absolute power over the animals and the farm. When the pigs overthrow Jones, they become the leaders. Eventually, Snowball gets run out of the farm, and Napoleon is leader. He takes the place of Jones and becomes a tyrant.
In the beginning, Old Major’s dream becomes the vision of Utopia. Old Major’s idea of Utopia is a place where man has no part. The closest the animals get to that vision is a few weeks after they overthrow Jones. Napoleon prevents this from happening when he becomes the leader. In the end, the pigs faces could not be distinguished with the humans faces.