The reader of George Orwell's allegory must always keep in mind that the author employs this genre as a tool of political satire, specifically, to criticize Stalinist Russia. With Napoleon as Joseph Stalin and Snowball as Leon Trotsky, Snowball is expelled from the farm as, like Trotsky, he opposes the bureaucracy of Napoleon/Stalin. Since Trotsky went into exile in Mexico and was later assassinated, Snowball does not return to Orwell's narrative, either.
Snowball is the true socialist; he works with the other animals and makes efforts to improve the quality of their lives through the creation of a windmill. However, the antagonistic Napoleon, who wants to be the sole ruler in complete control, foils the plans for the windmill that will produce electricity. For, just as a vote is about to take place in Chapter 5, Napoleon calls his ferocious dogs that chase Snowball,
One of them all but closed his jaws on Snowball's tail, but Snowball wisked it free just in time....slip through a hole in the hedge and was seen no more.
After Snowball has been exiled, Napoleon begins his propaganda campaign. He mitigates the part that Snowball has played in the Battle of the Cowshed, and he enlists Squealer as his propagandist who tells the other animals that Napoleon had only seemed to oppose the windmill building as
a manoeuvre to get rid of Snowball, who was a dangerous character and a bad influence.
Further, in Chapter 7, Squealer continues to use the name of Snowball in order to create fear in the animals and, thus, control them. When the black Minorca pullets (chickens), for instance, rebel and smash their eggs, and when negotiations go well with one farmer but not another, rumors begin that Snowball comes onto the farm and causes trouble. Any one who rebels is made to confess that Snowball appeared to them in their dreams and urged them to disobey.
In short, Snowball, who would have been a much better leader than the dictatorial Napoleon, becomes the scapegoat for all the problems on the farm. Certainly, he can never return, for Napoleon has fabricated his name as that of the enemy.