Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot. A satellite is, if nothing else, a fantastic thermos. A data center in space would necessarily rely completely on cooling by radiation, unlike a terrestrial data center that can make use of convection and conduction. You can't just pipe heat out into the atmosphere or build a heat exchanger. You can't exchange heat with vacuum. You can only radiate heat into it.
Heat is going to limit the compute that can be done in a satellite data centre and radiative cooling solutions are going to massively increase weight. It makes far more sense to build data centers in the arctic.
Musk is up to something here. This could be another hyperloop (i.e. A distracting promise meant to sabotage competition). It could be a legal dodge. It could be a power grab. What it will not be is a useful source of computing power. Anyone who takes this venture seriously is probably going to be burned.
His plan here clearly hinges around using robots to create a fully-automated GPU manufacturing and launch facility on the moon. Not launching any meaningful number from earth.
Raises some big questions about whether there are actually sufficient materials for GPU manufacture on the moon... But, whatever the case, the current pitch of earth-launches that the people involved with this "space datacenter" thing are making is a lie. I think it just sounds better than outright saying "we're going to build a self-replicating robot factory on the moon", and we are in the age of lying.