It all started with the differences between the animals, then led to the destruction of their freedom. The pigs took all of what they wanted without restraint to their appetite and their greediness. Altering the seven commandments was tricky because the other animals could have noticed. The pigs shouldnt have been so greedy, taking all the milk, apples, barley, and whiskey, it was a definite risk of having the rest of the farm overthrowing them. Snowball and Napoleon had different perspectives on how the future of animal farm was to be formed.
Napoleon was opposed to the building of the windmill, probably just because Snowball was all for the decision. By building the windmill and moving forward with Snowballs plans, there was an actual chance for less work fore all. Instead of equality, the pigs based working amounts on unfair conditions. Boxer did more work than all the others, but didnt get treated any better. The pigs excuse for not working was that they had to reserve their energy for brain power. So why didnt the other animals rebel against the pigs, maybe they were afraid to take a chance.
It was the worst accident of all, giving up their rights and freedom on a silver plater to the pigs. After all of what had happened, they saw there was no difference between their greedy leaders with their life long enemies.