Let's not view the Bible Students through rose colored glasses. Early Watchtower magazines point to Charles Russell's Studies in the Scriptures as the definitive authority on the Bible - and was the only publication being used by Jesus to spread "Truth".
If they (and later Rutherford's Jehovah's Witnesses) wanted to only print Bible study aids for people, they would have remained a Christian publishing house. Or they could have taken it one step further and created a New York mega-church.
Instead, by seeing themselves as the human representatives (and future kings) of God's heavenly government - with the only way, truth and (new) light - the WT leadership put themselves into a pickle. They gambled with the pickle and it has payed off - with an amazing amount of loyalty by the faithful membership to the WT organization and it's Governing Body.
In their eyes, remember, they don't make mistakes.
ginger