People have always chosen self consistent beliefs and ego preservation over factual information but the lines are getting extremely blurred.
So much easier to do that now.
Coherent narratives across groups are a relic of the past now. We choose our own realities.
It's damn easy to identify affiliation and your social media activity is out there for scraping and identification.
People who seed narratives need only a small cluster to affect everyone else and cause ripple effects.
Filtering is also way more expensive than just putting out more information.
This is a Schelling point that has adverse consequences for everyone involved except the players.
Centralised, open systems with information exchange freely possible has made cascading effects more severe.