Cofty has raised a very important point.
The "humble Bible study" of Russell and his companions was flawed from the start. Like Mormonism, which is a religion that sees writings as the starting point and measure for Christianity, Russell was influenced by Adventism's similar view of religious revelation.
Christianity (and its father religion Judaism) is not based on writings. Christianity produced writings. The books that became the New Testament were not the basis for its religious doctrines but selected due to their use in liturgical worship over the first 350 years of Christianity's existence.
The Christian canon developed because of Marcion of Sinope, a bishop that turned to Gnosticism, who taught that holy writ was the ultimate form of spiritual enlightenment or revelation and thus the only true measure of Christian doctrine. His canon, limited to a few of Paul's epistles, an edited-down version of Luke, and a rejection of the entire library of Hebrew works, moved Christian bishops to use their authority to set a standard for books that aligned with official use. The process would not be completed until the 4th century.
Judaism is (allegedly) based on a series of theophanies given to the patriarchs, to Moses, and the Great Theophany at Sinai, or so the claim is made. The Jews later composed the books based on the religious interpretation of their own history (a work that did not take shape until after the Babylonian exile ended).
Christianity originated in a similar manner. Based on a series of epiphanies based on the identity of Jesus of Nazareth, the Christian movement was born. Like Judaism before it, Christianity was not based on writings, rather it produced writings. Christianity, according to its own historical claim, is based on Jesus being the ultimate and final revelation in God, not the Scriptures. As so-called religious "truth" was found in the people of Israel, Christian "truth" was deposited in the community or "church" of Christian believers.
The Bible is merely a product of these movements, considered inspired and a revelation in and of themselves, true, but a testimony to something greater nevertheless. Russell's mistake was that of Joseph Smith. They, like Marcion of Sinope, believed and advocated the Gnostic teaching that the ultimate revelation of truth was found in the written word of religious movements, and not anywhere else in the community of believers that originally produced them.
Limiting themselves to the scope of what is composed on paper, all three men came up with odd and "unique" doctrines contrary to those taught by the communities that composed the texts. Without noting a deposit of faith that consists of both theological practice and written works, and accepting only the written texts, peculiar religions resulted. (In Smith's case he went one step further and claimed that an additional written text was also necessary.)
Limiting oneself to the Bible independent of the religions, cultures, peoples and theology that composed them is dangerous. It would be like taking the writings of the Dalai Lama and following them but rejecting his religion. It would be like basing a religion on Hubbard's "Dianetics" but claiming that Scientology did not have to be studied or followed. That is absurd, but it is what Russell did when studying the Bible and claiming that the Christianity that composed it and canonized it should be rejected, to curse the religion but praise its product, its book.
One does not have to be a theist to see the insanity of following the Gnostic rule that ultimate truth is found only in the written texts of a religion, but not in the religion itself. If the religion is false then its writings can't be true, especially when the religion came first and produced the writings, using its own authority to canonize them.