The book is based on the Russian revolution, the old major represents Karl Marx or Lenin, i think Lenin because lenins body was kept for showcasing after his death, so was major's skull. Snowball and Napoleon might represent trosky and Stalin. How a revolution, with initially good intends, strayed away from those principles with time, how people with power go currupt and enginner propogandas for their selfish needs and how the working class slave and the aristocrats live in luxury bcos of that, and all are excellently described in the story