How might the fact that the animals are having more celebrations even though their rations are being reduced work in Napoleon's favor?

Like any good dictator, Napoleon secures his power, in part, through ideology and spectacle. He promises that his plan for a windmill - which he had really stolen from Snowball - will make life better at the farm, and makes it a central point in his overall ideology. In other words, he uses it, among other such symbols, to assert power over his workers, and to quell any dissent among them.

Napoleon presents himself as a leader who always acts in the best interest of his fellow animals, while painting his opponents as evil allies of Snowball and/or Jones. In reality, Napoleon is a despot, and becomes more and more like Jones as the novel progresses. While this is readily apparent to us, the audience, the worker animals are distracted by such ideological tools as the windmill, which is presented as a sort of panacea for the farm's problems. They are also swayed by promises for better living conditions, an example of which would be running water in stalls. These tools mask the reality of the farm - namely, that Napoleon is subverting the revolution, and exploiting the workers for his own gain.

In addition, the workers are plied by celebrations, rousing songs about Napoleon, and Napoleon's constant invocation of past atrocities (that is, life under Jones). Indeed, Napoleon casts Snowball and his supposed associates as perpetual enemies of the farm; these terrifying figures are used to silence criticism. They help to keep the workers agitated, focused, and suitably patriotic.

Napoleon's ideological control only grows in scope and malice as the novel progresses. By the end, he has utterly reversed the aims of the revolution, and re-instates an authoritarian, exploitative system on the farm. He maintains his power, and his mirage of revolutionary zeal, even as he wears human clothes and lords over his former "comrades." This situation is best encapsulated by his final revision of The Seven Commandments: "All animals are equal, but some animals are more equal than others."

Thus, Napoleon's increasing despotism and hypocrisy are disguised by ideology and celebration. Over a period of time, Napoleon is not only able to whittle away his workers' knowledge of the original revolution, but even their desire to reach its goals. Whereas they had once dreamt of toppling Jones and ruling the farm together, they are now content to be simple, and to be less equal than pigs who now wear clothes and live like humans. That worker animals could celebrate despite their rations being cut is just one example of this terrifying, and realistic, process.