Many if not most beliefs widely held by the public are the result of deliberate propaganda campaigns. These propaganda campaigns are not motivated by spreading the truth but generally by somebody's financial interest.
Don't take my word for it. Read Propaganda by Edward Bernays https://www.amazon.com/Propaganda-Edward-Bernays-ebook/dp/B0097D76MG
Bernays is called the father of Madison Avenue and credited with inventing "making the world safe for democracy" in the propaganda campaign for World War I (they are still making the world safe for democracy hundred years later), inventing the diamond engagement ring, bacon and eggs, fluoridated water (his clients what to avoid liability for fluoride runoff so he convinced everybody fluoride was beneficial), The panel of doctors, and increasing cigarette sales 40% in one year by parading a few models up and down seventh Avenue smoking "torches of freedom" and convincing women to take up smoking, and many other things. He was also credited as a major inspiration by Goebbels. Goebbels is considered to have been extremely effective at convincing Germany to follow Hitler. Both of them were very open about how effective their propaganda was.