Isn't Starlink already basically a distributed datacenter in space? they have like ~9k+ satellites up there already at least according to: https://planet4589.org/space/con/star/stats.html.

what am I missing here?

I'd assume Starlink satellites do the minimal possible amount of compute required (thus power used, thus heat generated) to provide service. The builders of data centers are hungry for as many watts on Earth as they can source.