Not sure what thread you're referring to. I suppose maybe some people did think this wouldn't happen? But Zuckerberg publicly announced he was doing this flattening over a month ago. (Though we didn't the numbers until now.)
Seems like people were only skeptical of the specific dates given by an anonymous Blind user, just on the basis that it's an anonymous user. That's likely a good thing, even if it happened to be accurate!
They weren't skeptical that layoffs were coming aimed at a flattening, which makes sense since this was already announced by Zuckerberg over a month ago.
There were threads here, Reddit, and elsewhere. IIRC all pointing back to Blind. What I mention wasn't a universal opinion and apologies if I made it sound that way. But there was a much stronger segment than I would have expected thinking it was all a bunch of made up FUD