Self-deception and propaganda
It's easier to fool people than to convince them that they have been fooled. ( Falsely (?) attributed to Mark Twain.)
Propaganda works, because the people want to be deceived and manipulated. It gives people reasons to believe their own self-deceptions. They like to think that the society they live in is just and that the authorities are competent. It justifies the narcissism of the population and their rulers. One could even say that it involves a conspiracy where the elites and the ordinary people cooperate to establish a phantasy reality, consisting of a just society that is ruled by competent and good authorities.
Willful ignorance: Most people want to feel good about themselves and the country they live in. Therefore they want to believe in the goodness of society and their leaders. It makes them feel superior to live in a good and just society. Any half truth that makes this seem true is easily accepted. Good propaganda always appeals to and encourages the narcissistic tendencies of the people.
Reliance on authority and trust in expert knowledge: Most people rely on experts on things foreign to their daily live. These are government officials, experts, scientists, etc. These experts will always have agendas of their own, as well as agendas aligned with the institutions with which they are associated. Often they are allied to special interests and manipulate the truth. People in positions of authority are considered to be respectable. Respectable people are considered to be trustworthy. Hence they are easily believed, however outrageous their claims are.
Cooperation of the governed: For a society to function, people have to believe in it. They want their society to be just. Preferably, their society is the best possible in the world. Propaganda gives the population the excuse to believe this. Willfull ignorance does the rest.
Convenience and public apathy: It is more convenient to believe what one is told by the authorities, than to think critically about what is happening. People are not really interested in politics. Therefore lies work as well or better than facts. All that the politicians and other elites have to do, is lie and flatter the public. Even bizarre large lies work, provided they satisfy some desire or need of the public.
Open secret: Sometimes it is clear for everyone that the social system is unsustainable, but nobody talks about it. Certainly, nobody in a position of authority. Therefore everyone has the excuse of plausible deniability. We did not know it. One can remain passive and not take any responsibility. Conformity does the rest.
Conformity: The psychological mechanism of conformity ensures, that most people will not question generally accepted truths.
Blame the victims: Society is seen as just. Therefore projection mechanisms ensure that the victims must be to blame.
Scapegoating: Deflecting the anger and frustation of people with the system to a convenient minority. It hides elite failures and thusprevents unrest and rebellion. It is a combination of distraction from and denial of systemic failure.