In Animal Farm, how do the pigs become what they hated?

This question gets to the heart of one of the paradoxes of the story.  At the urging of Old Major, the animals rebel in a desire to seek freedom, but what they create is another form of servitude. At the head of all of this are the pigs. 

At the beginning of the story, the pigs are sincere.  We can see this in the commandments of animalism.  The laws are fair and treat everyone as equal, but as the story progresses, the pigs, who emerge as leaders, begin to change.  The text does not tell us why they changed, but we can see one key reason. 

Lord Acton's words are appropriate, "Absolute power corrupts absolutely." When the pigs experience the seductive allure of power they cannot resist.  In the beginning it is small; they steal the apples, but later they rule with an iron fist. They understand what the humans understand, the corrupting power of power. This is why the pigs make all the animals serve them. The most graphic and emotive example of this is what they did to Boxer, the most faithful worker on the farm.  When he could not work any longer, they sold him to the knackers to profit from his body being turned into glue. 

In conclusion, the corruption started small, but once it started, it accelerated and completely transformed the pigs into the very ones they hated. Absolute power did corrupt absolutely.