Chris, I think you have it right there!
As the prices of a few years ago began climbing, so did the number of cars coming out of the woodwork that could justify the spend of a full restoration. Resto costs moved up with the cars' values and the earlybirds got the buyers & cashed in on the excitement (speculators and those with FOMO). But it's supply and demand, and it appears that those with the money have got their cars and now there's a surplus!
Upside, those that thought they couldn't afford to own an early 911 now have a glimmer of hope!
Still glad I bought mine when I did (26 years ago) and still "drive it like I stole it". Which I pretty much did, when you consider what it's worth now, even with the current "dip".