How would the North Koreans profit from hacking grandma's PC?

It’s not the pc. It will be over the phone. They will call, use TTS with voice cloning to impersonate someone in their family, 5 seconds is all you need. Do a bank transfer to this address. Or click on this link we send you now over sms. You do a million of those.

Compromise the pc and use it a zombie for other ops. That's one example.