How is Orwell's novel (Animal Farm) a effective satire?

Please note George Orwell informs the readers before the text that it is 'A Fairy Story' and, interestingly, as an effective and amusing satire, nearly 100% of all characters are domestic animals talking, arguing, debating like human beings in English. Maybe, I think, Orwell imagines another world of animal dictatorship rather than the familiar ones in communist countries. Aesop, the great fable teller, might have done the same if he had been his contemporary.