There's an underworld that will buy stolen goods and part them out. And lots of middlemen who will help buy the goods. They don't need to ever turn on the device.
When armed robbers took my iPhone, it ended up in Ho Chi Minh City after 3 weeks. I'm guessing it went robber -> fence -> exporter -> foreign shop. Presumably someone there defeated the Find My iPhone lock or parted it out then.
I doubt these looters have access to middlemen, they’ll probably list it on ebay and hope some clueless person buys it