We also have to remember that Russell was a household name in those days, everyone knew of him. He was the Billy Graham of his day. The Judgesed that to his advantage. Even after all the chnages, people just associated the Watchtower with Russell. The Judge woould start BIble studies using Russell's wriytings, once these people got sucked in, he would do the switcharoo with one of his books and introduced new light.
Many of thodse Bible Students who did stay, were pretty nominal to say the least, or there were power hungry elders who didn't agree with Russell anyways.
RR