Why did women start to smoke? Why did people start buying lots of stuff they didn't actually need? What led to the Wall Street Crash? What led to Hitler's anti-democratic ideas? Where did the idea come from that capitalism and democracy cannot be separated?
A major part of the answer to those questions is: Edward Bernays (1891-1995).
He realised that people's inner desires could be used to make them do pretty much anything, if they were led to believe that performing that action might satisfy those longings. So, by a powerful PR stunt, smoking became seen as a "torch of freedom" for women, for example. These ideas about people's inner longings came from his uncle, Sigmund Freud (whom Bernays made famous).