An international operation against child sexual exploitation, supported by Europol and led by the State Criminal Police of Bavaria (Bayerisches Landeskriminalamt) and the Bavarian Central Office for the Prosecution of Cybercrime (ZCB), has resulted in the shutdown of Kidflix, one of the largest paedophile platforms in the world.
Discovery of this kind of thing is as old as civilization.
Someone runs their mouth, or you catch someone with incrimination evidence on them. Then you lean on them to tell you where to go.