Orwell is taking one step more here than in "1984". He describes the rebellion of the animals of a farm against the brutal, steadily drunken farmer who exploits and oppresses them violently. The usurpation against this rule of violence is successful. But to fight the evil it does not mean to attain the emergence of the good.
When in 1917 the Bolschewiki and Menschewiki overthrew Czarist Russia they removed a system that had brought for most of the people only hardly bearable conditions. In their place they set a regimen with an ideology that promised a wonderful future but created more terrible conditions than had ever existed before. The same goes with the animals on the farm. The freed ones installed a much worse rule. This happens not at once, it is a creeping and scaringly not avoidable process!
Is this the fate of any free order, that it deteriorates into dictatorship? Is this what Orwell wants to tell us? Not quite! He is about showing us that this is only inevitable when the conscience for freedom values is undermined. But then it might be an imperceptible process which is all the more successful in case of a skilled use of language. The individuals should get accustomed to the wrong and adopt it. This makes them assessable. In the end they have no more own voice and bleat "mee" and "moo" in lockstep until they can be lead to the butcher unresistantly. At first it is the turn of the unadopted, but in the end all others are in for it, even the rascals. They leave a desert behind. Enough examples in the younger history! Especially the 20th century has excelled in the realization of much promising but less promise keeping ideologies, whose devastating effects will last long.
Orwell`s book is an appeal to all to understand and treasure the freedom rights of man as superior sanctity of human possession and to restore them as the most precious good that people have. He hopes that man is wise enough to do it. It is a pious hope.
Freedom is always endangered if one or a group of people, a party, a majority etc. has the presumption to connote oneself as only owner of "truth". And freedom is getting lost, if it becomes a political will, transformed and applied by the power holders. Ideologies promise always to bring people to their true greatness. In truth they belittle them to unrecognizability. This can be seen in our times in Islam how it is lived by the Islamists where the individual is nothing, although promised paradise. Already Friedrich Hölderlin had said: "It were always those who made the world a hell who promised to make it paradise."
"Animal farm" is thrilling though you know in the beginning how it ends.