the few thousand Bible Students zealously distributed 10,000,000 copies of a tract featuring the subject “The Fall of Babylon”—a hard-hitting indictment of Christendom.
Somehow I doubt this. Did the Bible Students turn in field service reports in 1917? That's 3,333 tracts for each and every B.S.
They may have printed 10m copies of the tract, that does not mean they were read by 10m people. Keep in mind that toilet paper was in very short supply during this time period.