I was raised in a First Baptist Church, up until I was eleven, and then we moved to California and went to a Temple Baptist Church through most of my teens. I wasn't very involved, though. Mostly just Sundays. My parents made us go, but they did not attend very often, themselves. My dad was usually working on Sundays and my mother worked all week and I think was just too tired. But, she wanted to make sure we received a "Christian education" and upbringing.
I was baptized in the First Baptist Church at age eight. I had answered an altar call and I was very elated about it. So excited when the Pastor gave me a Bible of my very own. I still have it.
What I remember about the teachings of that Pastor was about how Jesus cleansed us of all sin. I remember it so well, because he always used magic tricks.
He had a vile full of black water, which represented our sins. He, then, put a dropper of something in the vile that made the water clear and clean again. That represented the blood of Jesus cleansing our sins. He was really good with kids. He also taught us about the Trinity with inner stacking dolls (like nesting dolls)...three of them of different sizes all nesting together to make one. He was a good teacher and all the kids loved him.
I don't think it is always not knowing the Bible or mainstream Christian thought that makes us vulnerable. I didn't know a lot, but I knew the basics. Sometimes, it's just a rejection of mainstream's interpretation. I have had so many LDS converts tell me that so much of "basic" LDS theology just "made sense". It made sense that the Father also had a body. It made sense that salvation is extended to everyone and can even be extended after death. It made sense and many people LOVE the idea that families can be together forever. Even the levels of heaven and God's long suffering view towards us, reminds them of how a good father should be. Eternal progression....that there is more substance to heaven than just wearing a halo and wings and singing hymns, as heaven is so often portrayed. There is a lot in the LDS religion that is attractive to people, even for some of those who might have an "intellectual" understanding of mainstream theology.