The transistors are experimental, and no one is building high-performance chips out of them.
You can't just scale current silicon nodes to some other substrate.
Even if you could, there's a huge difference between managing the temperature of a single transistor, managing temps on a wafer, and managing temps in a block of servers running close to the melting point of copper.
We don't use them on earth because we expect humans to be near computers and keeping anything extremely hot is a waste of energy.
But an autonomous space data center has no reason to be kept even remotely human habitable.