One of the hallmarks of totalitarianism is mass conformity to a psychotic official narrative. Not a regular official narrative, like the "Cold War" or the "War on Terror" narratives. A totally delusional official narrative that has little or no connection to reality and that is contradicted by a preponderance of facts.
Nazism and Stalinism are the classic examples, but the phenomenon is better observed in cults and other sub-cultural societal groups. Numerous examples will spring to mind: the Manson family, Jim Jones' People's Temple, the Church of Scientology, Heavens Gate, etc., each with its own psychotic official narrative: Helter Skelter, Christian Communism, Xenu and the Galactic Confederacy, and so on.
Looking in from the dominant culture (or back through time in the case of the Nazis), the delusional nature of these official narratives is glaringly obvious to most rational people. What many people fail to understand is that to those who fall prey to them (whether individual cult members or entire totalitarian societies) such narratives do not register as psychotic.