Comment by capyba

Radiation does not work “incredibly well”, especially at the temperature range of interest. Forced convection (what every large terrestrial electronics system uses, from gaming laptops to terrestrial data centers) is orders of magnitude more efficient at pulling heat out of electronics than radiation. Normally electronics generate heat in a very small area relative to the entire package size, and conduction+radiation offers many practical issues to efficiently dissipating that heat to deep space.

Source: many years of practical engineering experience solving this exact problem.