Olds like me wonder “what happened?”
The current theory goes like this
1. In the 90s the Internet, especially Google, became ad-click funded. (The click is important. Not funded by dollars sold, funded by click.)
2. Slowly Google and others discovered that emotionally extreme material generated more clicks. Again, clicks, not necessarily sales. (We don’t know if this is because the material selects for ad-clickers or encourages ad-clicks. I’ve probably clicked 4 ads in my life.)
3. Ads on kitten videos and white-nationalism and “viral content” got more clicks.
4. The algorithms encoded this knowledge and began tailoring content based on interest “hints”.
Lately researchers have been quantifying this. They found emotionally engaging content drives more clicks, and it is easier to invent that content than it is to find it. So the mass web became a tool for disseminating false content.
The effect is so powerful non-researchers see it in simple YouTube tests, aided in this case by a disaffected Google engineer:
https://www.nytimes.com/2018/03/10/opinion/sunday/youtube-politics-radical.html
Basically the dark side of humanity is amplified by Pay-per-click advertising business models.
The good news is there are obvious fixes. The same fixes used for other addictive social harms like tobacco. Regulation and taxes. For example, tax click-based ad revenue heavily.
To know the enemy is to understand the fix.