If you're a big FAANG-like company, you've seen workers make big gains in wages over the past year, and turnover rates have been increasing significantly during the great resignation. This isn't enough to sink you, but you don't like it, because it does eat into your margins a little. Of course you're still making massive profits, but workers getting any measure of power scares you. Imagine if this trend continues? Workers are only getting harder to find!
So what do you do? You can't walk up to all your CEO friends and say "Hey how can we go about paying everyone less? What if we all agree to lay off our expensive people at the same time? That way, we'll have a massive pool of workers to hire from that are all looking for jobs, and since they'll all be scared from having been laid off they'll happily take pay cuts. Additionally, it'll scare the hell out of the rest of the employees to see all their friends get blown up with no warning right in front of them. They'll want desperately to keep the jobs they have and won't leave!"
You can't say that because coordinated wage suppression is highly illegal (remember Apple and Google?). But wink/nod based wage suppression? Totally fine! If everyone just happens to fire their expensive workers at the same time but leaves no record of getting anyone to agree to it, it's perfectly allowed. This is not "copycat" behavior. This is all the CEOs recognizing what the game is and cashing in on it.
And better yet, there's nothing the tech workers can do about it! There are no real tech worker unions to speak of, and these companies know their workers have a highly libertarian bent who believe in the meritocracy myth, so there's no real risk of unionization no matter how bad things get. It's a pure win for them, with no real downsides, and the general consensus is that if they're smart they'll do this every so often to bring workers to heel. And given the pervasive attitudes about labor that I see among tech workers I don't see any reason to think that's wrong.