I'm sure some CEOs followed the Twitter lead, but I also think the entire industry was already shifting with regards to headcount. A lot of companies were hiring excessively going into that period and middle management bloat was a well-known phenomenon.
The overstaffing problem was painfully obvious at many of the companies I spoke too as a consultant during that time. They'd have bizarre situations where they'd have dozens of product managers, project managers, program managers, UX designers, and every other title but barely a handful of engineers. It was just a big gridlock of managers holding meetings all day.
One friend resigned from Twitter prior to anything Elon related, specifically citing the fact that it paid well but it was impossible to get anything done. Not all of Twitter was like this, but he was outside of engineering where he was one of scores of people with his same title all competing to work on tiny features for the site or app.
The pendulum seems to be swinging to the other direction, where companies are trying to do too much with too few people. I still see a lot of growing (or shrinking) pains where companies are cutting in the wrong places, like laying off engineers to the point of having more people with {product,project,program}-manager titles combined than engineers. I hope we settle out somewhere more reasonable soon.
This all rings true to me. I would take it a step further and say that during normal times throughout the history of corporate America, and especially in boom times, management will let fiefdoms grow fairly unchecked. Then an external trigger causes them to re-evaluate and that's when they're like "holy shit we don't need nearly this many people."
For those of us who have been around the block (i.e., are old), the only times I've personally seen companies aggressively cut personnel is during economic shocks (dotcom bubble and housing crisis as two examples) and only then were the companies running lean (I wouldn't even say they were running bare bones; it's the only time I've seen headcount actually optimized for the work being produced).
I think the Twitter purge was actually an example of a major trigger. Not on par with the previous two I mentioned (obviously), but it was so high profile that anyone in tech took note of it, which is why I made the original comment. I've never seen so much discussion around a layoff for a company that was not imminently imploding (some may say Twitter was about to implode, but if you said that at the time I think you were wrong regardless of the state of its financials).