In "Animal Farm," why does Napoleon allow Moses to return and tell his stories about Sugar Candy Mountain?
Napoleon allows Moses to return and tell stories about Sugarcandy Mountain for one main reason. Napoleon sees it as an opportunity to keep the animals subdued and docile. In allowing Moses to tell tales about a wonderful place far away, a place where rest is possible, they will be lulled into a dreamy state of endurance. They will be able to bare the burden of their lives on the farm with the hopes of a rewarding place of rest free from hard work and misery. Napoleon also sees that Moses will continue to stay and talk of this continually for a small allowance of beer a day. Moses then serves Napoleon unknowingly in keeping the animals under his control.
Further to the above answer, Marx called religion "the opiate of the people" so when the animals have something else to focus on, the atrocious conditions that they start to find themselves in are dulled by the promise of a better place. It's much like the idea that suffering on earth will be rewarded with heaven.
Napoleon allows Moses to return in Chapter IX "after an absence of several years" because his stories of Sugar Cane Mountain take the other animals' minds off the laborious conditions in which they now live. Believing in some place that is miraculous and wonderful (Sugar Cane Mountain in this instance actually represents "Heaven")--even though the pigs repeatedly and contemptously deny its existence--gives the animals the hope and the wherewithal to keep going in this life.
Moses--note the name--is the character who represents in the novel organized religion. He is upbeat, speaks of the "promised land" and is the only character in the novel who is allowed to eat without working. Napoleon probably considers it Moses' job to keep the other animals working on the farm through his preaching of a better place.