Its AI. Both AI actually being good now, and CEOs believing AI is good. Even at most big tech companies, L3 engineers were basically the "claudes" of their team (or at least, 80% of their job was basically to be a "claude"). You give them some well scoped, largely coding task (that you either delegate as part of a larger project, or just something you don't want to do), and then they execute it. Once they build trust and learn the system, then they get larger projects, and then promotions.
Places are still hiring juniors, but now the bar for them is just much much higher, because a large portion of the junior level work (i.e, execution on implementation details), is pretty much 80-90% done by some senior + AI at this point, whether people believe it or not. This was certainly the case at the FAANG I was at.
I don't know why this "COVID overhiring" rhetoric is still a talking point. Covid was over 5 years ago at this point, those "overhires" have already left or have been flushed out from all these layoffs. Are you telling me the "COVID" overhiring resulted in such a huge surplus that, 5-6 years later, they are still on the market?