People prefer a simplified view of history where people where dumb and ignorant even if it's often proven wrong. The reality is reasonably correct interpretations / ideas are often replaced by misinformation for long periods of time. The most obvious example is how do you lose a city. But, something as simple as crop rotation is often found, then lost then found again.

For a more popular example, two thousand years ago many people thought the earth was round based on a wide range of evidence. They even calculated the size of the earth with a fair amount of precision. A more striking example a scurvy cure was found, then lost and then found again over hundreds of years. http://idlewords.com/2010/03/scott_and_scurvy.htm

Might that not be because people were illiterate and any permanent record was very rare indeed?

Perhaps people were indeed dumb and ignorant. If no one told you all of these things since birth, would you have any idea that the earth goes around the moon. Supposing you are a knight, a farmer, a priest, a whatever, rather than someone dedicating yourself to the study of the stars, and no one told you ever that the earth goes around the sun, or even moves, would you ever find out or know at all and would you not believe the priest or whoever seems to know about the subject.

It is not that people are dumb. They just do not know. A doctor can tell me whatever he likes that sounds reasonable and as I would have no option I would believe him.

The most educated have learned quite a bit, but once you start talking about average populations you find a higher percentage of people in the US belied in evolution 100 years ago than do today.

And when you start taking about actual numbers you find that there are over a billion people that can't read living in the world today. Heck, due to the population increase there are probably more people in the world today that believe the world is flat than did in the 300 BC and there pictures of the thing.

>no one told you ever that the earth goes around the sun, or even moves, would you ever find out or know at all

It doesn't. Frames of reference - postmodernism for physicists.

Based on the literature such as from Plato and Aristotle, it seems ancient people were smarter than we are.