It may be an older term, but I’ve only started seeing it once I switched from Reddit. And I’ve never heard it outside of this website. I’m in my mid-40s as a frame of reference.
And I fully believe I could also have been living in a bubble, but I doubt I’m alone.
In a weird coincidence a show came out in 2016 before the election called BrainDead and the plot was that alien bugs are eating parts of our brains and causing hyper partisanship.
https://en.m.wikipedia.org/wiki/BrainDead