Was it because he became a much better conductor?

This means that better conductors have a reduced skin depth.

The overall resistance of the better conductor remains lower even with the reduced skin depth.

So liquid mercury is still probably a "better" conductor.

It's not going to conduct enough, you want a better conductor.

Glass is also a better conductor of cold than cardboard or plastic.

It has been observed almost exclusively in aquatic or amphibious animals, since water is a much better conductor than air.

More serious was the fact that helium was a far better conductor of heat than nitrogen.

Copper is a better conductor of electricity, and silicon makes for faster computer chips.

Plasma is a better conductor of electricity than copper.