[dvtrn]

I think they're just enumerating the entire address space

Even when you consider most calls now for SIP/VoIP platforms (which is where a lot of these scammers get their DID/phone numbers from) are charging fractions of a cent for outbound calls, enumerating and then dialing entire NPA spaces gets prohibitively expensive after even five minutes of dialing waiting for someone to pick up, even for the most dedicated of scam call centers.

Doesn't mean they aren't dialing randomly to see who picks up, just I doubt they're dialing entire phone number spaces wholesale.

What can be observed going on is these scammers quite literally trade lists of leaked phone numbers and email addresses and they actively keep track of who responds, and who falls for their scam before sharing the list with others.

Jim Browning (a popular youtube scambaiter and infosec pro) has videos where you can watch it happening with your own eyes.