I'd never heard of the "Dead Internet Theory" until you just posted about it. I Googled and skimmed an article. It seems some people who believe this theory to be true go as far as to believe that actors, politicians, etc on TV are or can be deep fake CGI? I don't believe that.
It depends on just which one you're reading about.
Some variations on the idea are a bit more... sane, while others are like "HOLY CRAP BASKETS, SKYNET RULES THE WEB"
It's one of those concepts that got onto the internet, and of course lots of people took the original idea and ran off with it in all sorts of directions and some of them ran straight off a cliff.