[Galatians4_16]

Built in a bunker under a mountain, so reduced airflow, plus need to hide heat signatures from outside surveillance?

Also, likely they had infrastructure available, from the nuclear power they use.

[kimmeld]

Cheyenne Wyoming not Cheyenne mountain.

[eptcyka]

Doesn't matter what conductor you use to move heat, the same amount of energy will have to be dispersed. And watercooling just implies more intermediate steps between the heatshield of the die and air. So I don't believe the heat signatures can really be helped.

[jeffbee]

This is a weather supercomputer, not a defense one.