Why do the animals confess to their crimes in Chapter 7 of Animal Farm?
For days after Squealer announced that Snowball was an undercover agent for Jones long before the rebellion, Napolean assembles the animals in the yard and suddenly orders the dogs to seize four pigs. When Napolean calls on them to confess their crimes, they immediately admit to being secretly in touch with Snowball, collaborating with him to destroy the windmill, and entering an agreement with Mr. Frederick. After confessing, the dogs rip their throats out. Various other animals then step forward from the crowd and confess to being influenced by Snowball. They are all slaughtered, and the surviving animals are deeply shaken.
The pigs initially confess their crimes because they are threatened by the savage dogs. Out of fear, the pigs attempt to appease Napolean in hopes that they will not be murdered. After the pigs are brutally slaughtered, hens and sheep are quick to confess minor crimes inspired by Snowball. Their offenses are ridiculous. From seeing Snowball in a dream, to urinating in a drinking pool, the animals willingly confess to minor offenses. The reason they confess is because they are paranoid. Out of fear that Napolean might find out about their transgressions, they confess in hopes of receiving a lesser punishment. Unfortunately, Napolean mercilessly slaughters each animal that confesses.
The forced confessions is a major part of chapter 7. In order to consolidate his own power, Napoleon orchestrates the demonstration of the forced confessions. The animals do not confess out of their own volition. Rather, they confess under extreme pressure and force, believing that a public confession could spare them from Napoleon's brutality. As is shown, it does not. Additionally, the forced confessions are also designed to divert attention from the food shortages and the challenges the animals undergo while living on the farm. Napoleon understands that ensuring their obedience is crucial during trying and difficult times. This is why he orchestrates the ceremony where he is awarded and those who have "betrayed" Animal Farm with voicing dissent or supporting Snowball are executed. The forced confessions also coincides with the teaching of a new slogan where "loyalty" to Animal Farm becomes all that matters.
The forced confessions mirror those of the Soviet Union under Stalin, especially the show trials of the late 1930s. It is inferred that a) the animals were threatened and tortured until they agreed to confess and b) the animals were so indoctrinated into the current ideology that they agreed to confess for the "good" of their country.