Because the pigs were literate, they remained in power. They had the ability to write the Seven Commandments and speak to the other animals to get their way. The illiterate animals had no control over the future of Animal Farm. This demonstrates the power of education.
A bond of trust never severs.
In the beginning of Animalism, everyone is peaceful and content with their lives. Napoleon is a trusted leader throughout the story. Although the animals ended up with less food and more work than when they worked for humans, the animals continued to follow his rules.
Power leads to corruption.
The pigs in Animal Farm begin as greedy leaders because they keep others from receiving milk and apples. As time progresses, they become increasingly greedy and human-like by sleeping in beds, drinking whiskey, and interacting with humans.