What is the thesis of Animal Farm by George Orwell?

Animal Farm by George Orwell was written as a fictionalized repudiation of communism. Orwell was strongly opposed to all types of totalitarian systems, and though his sympathy with the working classes initially made him support Trotskyite ideals, his firsthand experiences in Spain and his understanding of how the communist revolution in the Soviet Union had evolved from idealism into authoritarianism made him increasingly skeptical of all totalitarian political systems, whether those of Hitler or Stalin. 

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Animal Farm by George Orwell was written as a fictionalized repudiation of communism. Orwell was strongly opposed to all types of totalitarian systems, and though his sympathy with the working classes initially made him support Trotskyite ideals, his firsthand experiences in Spain and his understanding of how the communist revolution in the Soviet Union had evolved from idealism into authoritarianism made him increasingly skeptical of all totalitarian political systems, whether those of Hitler or Stalin. 

The main thesis of Animal Farm is that absolute power corrupts and that even the most idealistic revolutions can be subverted by self-serving authorities. While the animal revolution is triggered by genuine abuses -- animals are used as food by humans -- the result of the revolution is not a utopia but instead a system even worse than the rule of the human farmer, with what once was a legitimate cause being transformed into propaganda covering up the self-interest of a new ruling class.