Russell was late in the game of Pyramidology,others had outlined the idea long before he picked it up.
He was most impressed by that old fraud Piazzi-Smythe, who styled himself Astronomer Royal for Scotland, when there was no such position.
Chazzer wrote to Prof P-S and received a letter back which Russell proudly published in Studies in the Scriptures (the vol. about the pyramid), if you read it Piazzi-Smythe is actually very non-commital.
I kinda think it is no worse a theory than the latest overlapping generation tosh.