In the past people believed in lots of stupid things like "god exists", "the poor deserves its situation and the rich has earned its situation", "hatred toward blacks, Jews, neighbor country, homosexuals, handicapped and many more", "kings are good and democracy bad", "the strong country has a right to invade the week country", "the rich are evil and the poor saints" and so one.
So I think the idea that stupidity has increased is an illusion. The thing in the modern world is more that the tolerance for stupidity has decreased so we discover it more. The sad truth is also that each one of us believes in lots of stupid things but we are more interested in finding errors in other when in self improvement. Like Jesus said, "and why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye?"
Maybe, in the past stupid was mainly reserved for people who knew very few facts. Knowing or having access to facts was much less common before the internet. So people used to argue about facts. But since those arguments were about facts, they always died down (someone was right and someone wrong) and you did not have a feeling of "expanding stupidity".
Since access to facts is pretty much universal now, people have started arguing about values. If someone states they have different values than you, you call them stupid. Since no one is right an no one wrong, the arguments don't die down and you perceive expanding stupidity.
Stupidity is about lacking intellectual capacity (not necessary the same as IQ, also things like not being interested in thinking, or lacking necessary facts about a subject can give you a lack of capacity.)
Both stating wrong facts and having ridiculous values is correlated with being stupid. So I do not really see how the Fact-value distinction can be used here, stupid people fail at both.
(https://en.wikipedia.org/wiki/Fact-value_distinction)
I think this is undoubtedly a relatively large contributor to the perception of modern stupidity.
Additionally, I read it as part of some of the written hypotheses, but, upon rereading, I don't know that the exact conditions are captured particularly well in any of them.
So I think the idea that stupidity has increased is an illusion. The thing in the modern world is more that the tolerance for stupidity has decreased so we discover it more. The sad truth is also that each one of us believes in lots of stupid things but we are more interested in finding errors in other when in self improvement. Like Jesus said, "and why do you look at the speck in your brother’s eye, but do not consider the plank in your own eye?"