Amplifier damage caused by failed power supply capacitors
A more likely scenario is that the short circuit damaged the power transistors so they failed short circuit, and they in turn caused the capacitors to fail. If the amp uses discrete power transistors, these will be replaceable. If it's a custom IC or hybrid module, you're less likely to be able to find replacements.

Resistance measurements on the transistor pins (compare with the "good" channel) looking for collector-emitter shorts may help confirm this scenario, and show which transistors need replacing. Or if both channels measure the same, you may be lucky and re-capping will be OK.