How is Snowball used as a scapegoat?
In Animal Farm, Snowball is routinely used as a scapegoat after he is expelled by Napoleon. In Chapter Seven, for example, it is declared that Snowball is hiding nearby and "secretly frequenting" the farm every night. In these visits, it is alleged that he carries out all "sorts of mischief," like breaking eggs, blocking drains and trampling the seedbeds. In fact, every time something goes wrong on the farm, the animals immediately blame Snowball:
"Whenever anything went wrong it became usual to attribute it to Snowball."
This leads Napoleon to order a full investigation into Snowball's so-called acts of sabotage. Squealer concludes that Snowball is in league with Mr. Jones and that he has a number of "secret agents" on the farm. By scapegoating Snowball in this way, Napoleon is able to carry out a number of executions later in this chapter, on the pretense that he is ridding the farm of its enemies.
Snowball is easy for Napoleon to use as his scapegoat because Snowball is not there- he was "expelled" from the farm. Any time something goes wrong on the farm, the windmill falling apart, things disappearing, etc. it's easy to blame Snowball because he is not there to defend himself and the animals don't know any better so they believe it. It's also easy to use Snowball as a scapegoat in the sense that when his ideas are stolen by Napoleon, no one can say for certain that they were Snowball's ideas first. Napoleon even goes as far as to call Snowball a criminal and he relies on the ignorance of the animals and their inability to remember correctly to get them all to believe these things.
A windstorm knocks down the windmill which devastates all the hard work the animals have put in, all for the hope of making their lives easier.
They are told that it was Snowball's act of vandalism that did this to them. They even find that there are pig's tracks to back up the claim. A reward is offered for his capture. Instead of accepting defeat, the pigs try to instill anger to drive the animals to work even harder.