J. Edgar Hoover re-established the Millennium Group.
The retcon of Hoover founding the group instead of it existing since the Middle Ages can be explained. The group was likely shut down by the House of Un-American Committee or Joseph McCarthy, accusing them of being communists. Hoover, a member of the group beforehand, re-formed it as a "criminal investigative consulting firm" after the Communist Witch Hunt died down. The Frenchman was a member of the Millennium Group.
He has the same visions as Frank. He left the group, believing he was given a mission to kill people he thinks are evil.