I'd argue the D4s and D5 may be some of the best high ISO cameras I'm aware of maybe surpassed by that one canon video camera that can seemingly see in the dark (sorry I'm mobile) and the D3s. I think the lower numbers produce nicer looking max ISO noise but that's all preference. Sony has the A7s as well but as with some of these the overall resolution isn't extreme.

How does the age of the camera influence physics? The only thing that really helps would be increasing the aperture.

Lower noise sensors and better image stabilization for longer exposures

Newer backside illuminated sensors have better quantum efficiency and are sensitive to a greater fraction of the light hitting the sensor thanks to the lack of electronics physically blocking the photosites. Not to mention advances in read noise and other stuff (less relevant for high end CMOS sensors for short exposures, which are shot noise dominated, but still).