Totalitarianism begins as dream. It ends in nightmare, the destruction of the individual. Hannah Arendt, a Jew who fled Hitler, analyzed the commonalities of communism and Naziism in her book, The Origins of Totalitarianism. 

Life doesn't make a very good story. It's inconsistent, irrational, unfair. We can end up feeling alienated alone, as though we don't matter. The totalitarian Big Lie provides an explanation, naming villains and identifying a narrative for pursuing justice. It seems to make sense of a senseless world. Through its actions, its continuous movement, it proves its lies true. 

Alone and insulated from the real world, it's easy to fall for the lie, to follow chains of logic that lead somewhere terrible. And one need not be alone. You may hear that the movement is violent and extreme, but the people you actually encounter are sympathizers or allies: normal, decent people who share some of its ideals and goals. They are the gateway to the movement. Once your are inside, they serve as insulation: even as the you get closer to the extreme core of the totalitarian ideology, you are always surrounded by people who make you feel less extreme than you are. it's an echo chamber. It is easy to believe that everyone (except for very bad people) agrees with you when the only people you encounter share your views. 

The ideology is total, because it claims that everything is political. It erases the distinction between public and private. Everyone is first and foremost an agent in pursuing the inevitable, just course of history. Even when the movement turns on them, believers often submit: a life given for the cause is better than a life (or death) without meaning.