I can't speak formally for any of the companies, of course, but I suspect like another commenter said, its an opportunity to cut fat. Beyond that, the last two years saw many tech companies grow stupid-fast. For example, Snap hired more than 50% of their pre-layoff workforce since start of the pandemic. Google, Meta have both doubled headcount in a similar (slightly longer) time scale.

I suspect that despite being rich, headcount is expensive. If the median googler makes 300k, it probably costs Google 500k to employ. A team of 100 is $50M! A news article claimed google hired 10k people in Q2, so that'd be $5B in commitment (probably actually less, but on that scale). Doesn't take many quarters of that sort of growth to outpace income.