Why do the animals of Animal Farm confess to being traitors?

Things are going horribly wrong with the Animalist experiment. There are chronic food shortages on the farm; everyone has to work harder for fewer rations; and the rickety old windmill has collapsed. But Napoleon cannot admit that he is any way responsible for what's happening, despite being dictator. So he creates a scapegoat, namely Snowball. Napoleon makes out that Snowball is the evil genius behind everything that goes wrong on the farm. And any animal found to be in league with Snowball is history.
Napoleon assembles all the animals in the yard. There follows a grotesque, bloody spectacle of false confessions and summary executions. So why do the animals confess to something they haven't done? There all kinds of reasons. Fear would be one of them. Although the animals are not actually guilty of anything, some of them are worried that if they don't confess, they'll end up getting in trouble sooner or later.
However, the most important factor is that the animals, for all their troubles, have come to believe in the ideals of the Animalist revolution; they've invested themselves body and soul in its success. If things are going wrong, then it can't be the fault of Animalism; it must be because of conscious acts of sabotage. According to the dominant ideology, the individual is ultimately of no importance; the collective is everything. This inculcates a mindset of individual sacrifice for a higher cause, and it is this, more than anything, that prompts animals to come forward and confess to crimes that they never committed.