There have been a number of historic events that had large measurable effects on human intelligience.
Invention of libraries
Invention of public schools
Building of large universities
Invention of leaded anti knocking compounds in fuel
Policies which reduce or limit access to said public education
Covid-19 longterm impact on cognitive ability
Policies which cause intellectuals to flee to other countries
Even if the average persons intellect is in decline, things are getting more complex. Society continues to advance in the long term, equity improves, crime and disease rates go down.
Personally, I really hate this diagram. It feels like its used far more to tar a huge part of the population as "weak" and therefore not worth considering.
Now, there us an element of truth to this in that it probably is not a coincidence that fascism is on the rise right after the generation that fought in WW2 mostly died off. But I'd much rather blame the current problems on thr handful of plutocrats who have been sabatoging things for gerations now, than claim its due to some ineitablilty with strength and generations.
Yes, just now everyone has multiple platforms to show everyone just how fucking moronic they are. Before the internet you’d have to be in close proximity to someone to be able to tell they were brain dead now we can just see the dumb shit these fools post from anywhere.
I feel like social media has definitely made things worse. Stupid people can find each other and make each other more stupid. Start whole "flat earth" or "anti-vaxx" groups and conventions. Before social media, you might have a couple idiots in your office or village, but they'd typically be surrounded by more average people who could level them out.
There was also a disaster in how reading was taught in the US for the past 20 years, so a lot of kids didn't really get taught to read well. ( https://features.apmreports.org/sold-a-story/ , if you're interested )