I have no evidence of this, but the ad load on the returned results has gotten way higher. In theory, ranking sites that display Google ads higher would be a very easy knob for Google to turn to increase profit. The SO scrapers probably have Google ads on them, making them more profitable for Google.
10 years I gave up on a large project where I rehosted and organized dead Usenet forum content because Google's dupe-penalty detector was too good and too aggressive for content that you could barely find beyond a six-year-old cache hit where the origin website was long gone.
Meanwhile these Stack Overflow scrapers are just `<html>{copy-and-paste}</html>` and the same domains are still alive despite years of cloning.
Turning the knob one way explicitly might raise some anti-trust concerns, however the same motivation can be used to avoid turning the knob the other way and this can be done much more sneakily without leaving clear evidence - simply don't allocate budget/etc to projects that would turn the knob the other way and you're done.
I've noticed this with youtube. Even though I'm on desktop with an adblocker they repeatedly autoplay the same video with a creator embedded crypto promotion at the beginning (especially when it would be plausible to infer I'm asleep from user interaction and clock/watch time). Must be getting a cut (plus scamming the ad buyer).
