Hmm, let's read that entire paragraph.
8. What accounts for the remarkable growth in Jehovah’s modern-day organization?
8 There has been remarkable growth in the number of God’s servants because Jehovah himself is backing his Witnesses.(Read Isaiah 43:10-12.) This increase was foretold in these prophetic words: “The little one will become a thousand and the small one a mighty nation. I myself, Jehovah, will speed it up in its own time.” (Isa. 60:22) At one time, the anointed remnant were like “the little one,” but their number grew as other spiritual Israelites were brought into God’s organization. (Gal. 6:16) Because of Jehovah’s blessing over the years, the increase continues with the gathering of the great crowd.
The rate at which the members of Jehovah's Witness membership (those of the earthly hope) is growing is right around the rate that the world population is growing. The rate at which the "anointed partakers" is growing is much higher!
So what really accounts for the "remarkable growth in Jehovah's modern day organization"?