I think it’s public schools and media consumption.
There might be validity to that. For so many people nowadays, it involves letting other people do your thinking and your work for you. I remember the internet being a do it yourself endeavor up through the 2000s before Twitter and Facebook, and YouTube, and the other platforms took over. The reason for the other platforms taking over was because they were easy in comparison and they often did most of the work for you as opposed to you writing out the HTML or the Java yourself. Since it didn’t require as much thinking but way more being a passive audience on the internet, it isn’t too far of a stretch that many people ended up thinking less, and didn’t need as much intelligence or thinking to get by in life.