This sounds like the kind of thing someone says which sounds true and compelling in an exciting way, but is actually totally bogus :) Do you have any evidence of this being true?
Here’s a recent example: They investigated guys who robbed Verizon stores, which led them to guys who bought phones from those guys, and wholesalers who then bought phones from those middlemen and exported the stolen phones to Hong Kong and Dubai. The value of the fraudulently obtained or stolen phones in the above case is about 100 million dollars and has resulted in various leads ranging from rogue carrier employees unlocking phones to drug cartels using cash to buy phones as part of a trade based money laundering scheme (see also https://storage.courtlistener.com/recap/gov.uscourts.cacd.85...)
You can find lots of examples of this work-your-way-up approach in the history of organized crime; https://en.wikipedia.org/wiki/Bonanno_crime_family#Downfall_... serves as a decent example, leading to the family's boss himself turning into an FBI informant.
Here’s a recent example: They investigated guys who robbed Verizon stores, which led them to guys who bought phones from those guys, and wholesalers who then bought phones from those middlemen and exported the stolen phones to Hong Kong and Dubai. The value of the fraudulently obtained or stolen phones in the above case is about 100 million dollars and has resulted in various leads ranging from rogue carrier employees unlocking phones to drug cartels using cash to buy phones as part of a trade based money laundering scheme (see also https://storage.courtlistener.com/recap/gov.uscourts.cacd.85...)