Easy answer ... the WTS. and J Rutherford was still participating in Pyramidology in 1918.
Other answer ....... the WTS proclaimed that Jesus set up a earthly and heavenly Kingdom in 1874 prior to 1918.
The 6000 year dating calculation of mankind existence that C T Russell used was a false incalculable calculation, it was used 60 years further in the late 1960's by the WTS's leaders to create 1975.
These were nothing more than marketing strategies to heighten attention to the literature the Watchtower Corporation published , thats a undeniable and truthful fact.