https://blog.hootsuite.com/facebook-algorithm/
see this
only 5% reach on each facebook post
which means you only receive/view about 5% of the content posted by your friends
that is how the echo chamber is built
with 5-10% of users creating 90% of algorithmically generated content for the social media feeds
https://freshwater.co.uk/thoughts/timeline-of-google-algorithm-changes/