The radiator panels on the ISS are 2,500 square meters in area. The radiator panels are 645 square meters.
Most of the proposals for space-based data centers have ended up focusing on plans to place thousands of individual satellites into orbit, not just one big space station with everything packed inside it. Scott Manley recently did an analysis of the cooling requirements, he worked through all the numbers and explained how it works, and there really doesn't seem to be a problem here.
That article was incorrect, then. There are many satellites already in orbit that have computers in them - basically all of them do, nowadays - and cooling them is a well understood engineering problem.