In Animal Farm, Orwell demonstrates that revolution is impossible to achieve when power is abused and when ignorance prevents the citizenry from acting.
When Old Major opens the novel with his talk of Animalism, it is rousing because he ensures the awareness of all animals. Old Major insists that all animals are cognizant of how "Whatever goes upon four legs, or has wings, is a friend." He also insists that all of the animals accept "in fighting against Man, we must not come to resemble him. Even when you have conquered him, do not adopt his vices." Part of the reason why the call to revolution is so successful in Chapter 1 is because he displays power as inclusive of all animals. None are ignorant as to what is happening because of a transparent call to revolution that applies to all, including "the wild creatures." Power is not abused because it is shared and inclusive.
As the narrative progresses, Orwell shows that ignorance and manipulation are why the revolution fails. Once the pigs assert power in the wake of Old Major's death, they keep power to themselves. The pigs are responsible for the decisions on the farm and, through Squealer's attempts, are able to keep everything to themselves. At the same time, the animals are steeped in ignorance. Boxer keeps absorbing that he must "work harder" and that "Napoleon is always right." The sheep simply continue their bleating, while Benjamin is disengaged from action. The animals are ignorant of needing to change their leadership. The result is that nothing really changes and the power imbalance and exploitation continues. In this reality, Orwell concludes that the revolution fails because of a fatal combination of ignorance and the abuse of power.