Lots of great answers here.
I think one under mentioned cause is the effect of social media algorithms.
All major social media platforms use machine learning algorithms decide what to show in your feed. The algorithms are programmed to show you the things that have historically kept you on the site longer.
It’s human nature to upvote/read/support/engage with the things that agree with our world views, and downvote/dismiss/disengage/discredit the things that disagree with our worldview.
These two facts combined result in you seeing more of the content that aligns with your worldview, and more of the content from people who share your worldview. We’re all funnelled into communities of like minded individuals that repeat what we already believe, reinforcing whatever that is regardless of how factually correct it might be.
Dissenting information that might cause you to reconsider your position or become more politically aware is automatically filtered out.
And it’s not just social media either, even the algorithms behind search engines display this behaviour.
Long before social media existed, Google was tailoring search results to match the things you tend to click on. If you searched for news and typically clicked on the headlines biased towards one side or the other Google would start ranking site with that bias higher.
This wasn’t intentional (at least not originally) it was just a side effect of the algorithm, trying to figure out what you were most likely looking for.
For someone who, for example, believes the Earth is flat. If they were to type “is the Earth flat?” Into a search engine. They are much more likely to get results that “prove” the Earth is flat, then a person who believes the Earth is round, because the algorithm knows that they tend to click on articles that “confirm” the earth is flat.
Algorithms used by social media and search engines today, make it genuinely difficult to maintain a balanced worldview and find unbiased answers to any question. They are all designed to keep you engaged, And it is human nature to engage more with the things we agree with, regardless of truth.
