Why Did Napoleon's Leadership Corrupt?

Why did Napoleon's Leadership corrupt ? In the book Animal Farm ,Orwell changes the leaders of the book many times I feel he does this to show how every leader runs the farm in different ways ,but one really stood out to me the way Napoleon did when he was in control and the drastic changes he made to the farm. Napoleon became a leader because of his hard work on the farm, this happened towards the end of the book. All of the drastic changes mostly happen at the end of the book when Napoleon was in charge.

When Napoleon became the leader of the farm he wanted everyone to work harder, he also did not make everything equal for all the animals the pigs were given more food. Most of the changes Napoleon made happened after the expulsion of Snowball.