But I think there's solutions to the waste heat issue
https://www.nasa.gov/centers-and-facilities/goddard/engineer...
Like on the order of tens or hundreds of watts but -100C.
Dissipating heat for an AI datacenter is a different game. A single AI inference or training rack is going to be putting out somewhere around 100kW of waste heat. Temps don't have to be cryogenic but it's the difference between chiselling a marble or jade statue and excavating a quarry.