The populace is so brainwashed/naive that they can't even conceive of the POSSIBILITY that their sociopathic/psychopathic 'leaders' are capable of doing anything to keep and expand their power...if people think that 'conspiracies' to manipulate the public into ceding more power to their 'leaders' are 'impossible', then no amount of evidence to the contrary will ever change their minds.
Most people aren't sociopaths/psychopaths so can't get their minds around the FACT that there are, indeed, deeply disturbed individuals out there who are incapable of feeling empathy for others & actually LIKE hurting other people...the smartest, most conniving, most ruthless of these kinds of people are NATURALLY going to gravitate towards positions of power that allow them to play out their sick desires of dominating/hurting other people.
So, while people on some level realize that sociopaths/psychopaths exist, the idea that these sickos could claw their way to the top of the political-power structure to become Senators, CIA/DHS/FBI/NSA Directors, Cabinet-level administrators, Judges, and, yes, Presidents either doesn't occur to them or is so awful to contemplate that their minds go into cognitive-dissonance mode.