I think that the type of intellect is the issue. Why?
At the start, only highly technical types dominated the Internet. Other types existed, but were the minority.
And at the start, the Internet had more, tech only content. Sure, there were funny memes, other silly things, but cat videos didn't take up 99.99% of all non-porn traffic.
This type of personality tends to do lots of research, read a lot, where as most of the population never picks up a book, and very rarely reads. And while the Internet forces the average Joe to read, reading a headline is all they do. And can even tolerate.
(Note that UN national literary rates, are based upon what a 7th grader can read. An average one too, not a particularly bright one.)
Couple this with tiny smartphone displays, where a three paragraph news article looks like a massive wall of text...
And, no text reflow in mainline phone browsers due to agendas...
And most Internet commentators aren't even able to listen, or understand, the other side.
One of the most popular communication methods forces tiny little sentences, forcing even the highly literate to write like Captain Kirk, in halting, disjointed sentences!
Then, couple all of this with something else readers / those who enjoy learning, do? Why, they learn history! The history of why you never do this or that, or why thing $x leads to bad outcomes time and time again, which provides significant context to the world.
In short? The Internet now belongs to the masses, and that is why it changed.