Yes, that was the turning point. You have to remember, in addition to the end of ZIRP this also happened after a few years of an extremely strong employee's market. Jobseekers were asking for and getting some pretty wild packages.
Elon's actions were a clear signal to the industry and investors that it's time to "fight back" and show the labor market who's really in charge.
It goes beyond Elon. PE was (are?) pressuring Google to lay off more employees because their pay was so high. And the Fed said that worker pay was "too high," in the context of inflation.
Basically, the ownership class was pissy that some people were able to actually get away from exchanging time for money.
Yep, precisely! But all that was happening on a slow burn. Elon's deliberately public actions at Twitter were a (very intentional, I suspect) match to the powderkeg.