What we believe is often not determined by our own faculties of reason, and this holds true for the smartest, and most aware of us.
Bernays is effectively the founder of modern advertising, and although he doesnt discuss his role in it, he was incredibly influential in things like women smoking cigarettes. A descendant of Freud, he focuses on the psychological desires of individuals (following the masses, confirmation bias, etc.), and using mass communication to uncover and bend those drives. Basically you can think about him as the founder of PR, but if that guy was evil.