Asside from the other excellent comments on power consumption, cooling and radiation. One point I didn't see being made in the comments much is maintenance costs.
Now I don't find myself in the facility of a data center often in daily life, however I do know that medium to big data centers require 24/7 hardware replacement. I believe this is what those 5 guys with the bikes and scooters are doing in every data center. That would be very difficult, near impossible in space (with the current space fairing infrastructure).
Can SpaceX not just say "OK, GPU #7 on satellite #15872 is broken, don't use it" and just accept that they're now overbuilt on power/cooling for that sat?