I think the big gain came from "ReSTIR". The previous games released with RT "remasters" like Quake 2 have only a few lights that need to be traced per frame. ReSTIR apparently can optimize how rays are traced and allows for far more light sources to be visible.

This is where the performance gain for the 100s of lights Cyberpunk might have in a single frame comes from.

https://research.nvidia.com/publication/2021-06_restir-gi-pa...

There is a "Digital Foundry" video which mentioned it.