Social media, and the tech companies at large, facilitated and created and _exacerbated_ this problem. Its been known for a long time.
https://www.ted.com/talks/eli_pariser_beware_online_filter_b...
Whereas previously people were not so hyperpartisan-ized by social media, they are now. You could have a debate on various topics with your neighbors and friends, but now its two camps. Disagree with me? You are a nazi, or a communist.