[sp332]

I think over the years, there have been enough news articles about Facebook recommending conspiracy theory groups for most employees to have a good idea of how engagement was driven. Every news organization researched how to get clicks, so it's not a secret that articles with more-negative headlines get more engagement. Remember the employee walkout? There is plenty of awareness within the company about how the sausage gets made.

[scns]

My guess would be, that weighting negative stimuli higher was an evolutionary advantage. The individuals that listened birds did not survive, those wary of predators did.