Radiators work because they have something to radiate heat into. Space is famously empty, so a radiator the size of a planet would only work as a heat sink until the total heat in the system was high enough to make everything glow like a heating element, at which point you dump waste energy as visible light.

This is what I’ve been tearing my hair out over any time this comes up. If you put a computer in space it will heat up until it achieves incandescence. Which is bad for the performance.

Like every industry does, and gets away with it if they keep it looking competitive.