However, one cannot use Reddit currently without seeing 42 smiling pictures of a murderer, with thousands of fawning comments.
Many are bots, manipulating people on social media. Unfortunately, too many people are pulled into that bubble and become convinced it represents reality. It doesn't anymore than the flood of Harris posts that suddenly stopped on a dime election night, leaving millions of young people wondering where all the support went (not realizing the support was never there to begin with).
I don't think you're describing any particular political phenomenon though. We saw the same thing happen in 2016 and 2020 overnight - people go from Facebook pundits to sheepish and sore losers in just 12 hours. Bots certainly play a role in all this, but I think you're wrong to blame them as the deus-ex-machina when human behavior explains it all just fine.
Support bases are real for Luigi Mangione and Harris in the same way it's real for MAGA and Elon. People are truly sucked into the cult of personality because it's big, and they don't understand how to contextualize politics outside of celebrity. In a world where people virtue-signal on their favorite politically-aligned platform, it's not hard at all to imagine the majority of this support being entirely genuine.
A lot of people thought the "Stop the Steal" folks were bots, until they showed up and rioted and subsequently hid their identities out of fear that they'd be lambasted for supporting an anti-populist movement. In a post-Jan 6th world I don't quite understand how you can still blame bots for stupid opinions that real people clearly hold.
Most of America (somehow) didn't know what they were voting for and just believed the empty promises.
See the recent regrets of steelworkers and trends of people searching "can I change my vote".
Oh yeah, and all of the people mad that President Musk is gonna increase H1Bs.