In Animal Farm, the idea of the revolution comes from Old Major, a 12 year old prize white boar who has a vision in a dream about the way the animals should be living. He comes up with a set of rules for the animals to follow, which include that man is evil and an enemy to all animals. He also tells them that all animals are equal.
"In Animal Farm the animals begin by proclaiming the equality of all animals. The classless society soon becomes divided as preferential treatment is given to the pigs. First, they alone are allowed to consume the milk and the apples which Squealer claims they do not really want to take, but must to preserve their strength."
Once the animals stage the revolution, confronting Farmer Jones and his men and successfully chase them off the farm, they are very happy believing that now they will control their own lives and that they will have better lives than when Farmer Jones ran the farm.
As with any revolution, there is a power vacuum once the old authority is removed, and inevitably, some members of the revolution will assume that they are the best suited to be the new leaders. Absolute power corrupts absolutely, the saying applies to Animal Farm, because as Napoleon and Snowball start to access the farm's operation without the farmer, and Snowball starts to make all kinds of plans to improve efficiencies, Snowball is a symbol for Trotsky in the Russian revolution, Napoleon, a symbol for Stalin, has other ideas, namely to be in complete control of the animals and the farm for his own gain.
"Although the novel is written in direct response to his bitter disappointment that the Russian Revolution, instead of establishing a people's republic, established an essentially totalitarian state, its continued relevance is possible because his criticism stands against any and all totalitarian regimes."
The ideas of the revolution that are supposed to provide greater freedom for the animals, end up imprisoning them in a world governed by the tyrant Napoleon who exploits, starves and punishes the animals with greater severity than Farmer Jones ever imagined.
"He, like many critics have since, pointed out the similarity between conclusions drawn from Orwell's text and the famous aphorism of British historian Lord Acton who wrote, "Power tends to corrupt; absolute power corrupts absolutely."