“The receptivity of the masses is very limited, their intelligence is small, but their power of forgetting is enormous. In consequence of these facts, all effective propaganda must be limited to a very few points and must harp on these in slogans until the last member of the public understands what you want him to understand by your slogan.” ~ Adolf Hitler
And so began the task! In order for the powerful to control the masses, a compliant populace is required. Those who hold the real power over the political class and media have been successful in their efforts to gain this control. This has always been, and given the human condition, will most likely always be. If only it were not so easy to fool the crowd, all could be different. But then, any crowd is easy to please, and easy to fool, that is the nature of the beast that is the mob.
Common people, generally speaking, believe what they want to believe, and most often choose the most comfortable path. Personal conflict due to the shattering of accepted norms is avoided at all costs, and any truth that can cause doubt is quickly rejected.