That's surprising to me.
I'm sure there are many people (including me) who don't know some important details of the history, but hasn't almost everybody heard the thing about Jesus forgiving us of our sins if we ask and so forth? A person doesn't need to know all the details to make an informed decision against being a Christian IMO.
One of the things I've noticed in the 13 or so years since I started really looking into theology and the history of Christianity is that a lot of Christians, not just "nominal" Christians but regular church-going Christians, were a lot like I was before I started really looking into things. I grew up in a thoroughly Christian environment, church every Sunday, and mid-week services as well, attended Christian schools from K - 8th grade, in high school I attended two different youth groups, from my own church and also from the church most of my friends attended. I had a good knowledge of the stories from the Bible, and all that. But what I lacked was a real education about my religion.
I realized this when I was about 19-ish(?) when I started wanting to learn more and came to a startling realization while reading my Bible to discover that rather consistently throughout the New Testament it talks about the Christian hope being a future resurrection from the dead. At no point had anyone talked about this, or certainly not that I could recall. When I spoke to others, including my father, I just received a confused look. When I decided to see if I was maybe just misinterpreting what I was reading by looking at what Christians have historically said for the last two thousand years, I discovered that it's what
all Christians have said for the last two thousand years.
So how come I had been taught that the Christian hope is, when I die, depart from the world as a disembodied soul into Heaven and spend eternity as a bodiless spirit?
It's because this, for some reason, is what many churches teach, it's part of the narrative: Believe in Jesus and go to heaven when you die, don't and go to hell when you die.
What I began to notice was that there's a kind of "popular religion", what many in the Church and culture receive whether explicitly or implicitly through a kind of osmosis. I think about some of those old Tom & Jerry cartoons, in at least one there's an escalator going up into heaven and one going down into hell--heaven was that place with pearly gates and streets of gold, the departed spend their eternity there as part of the choir eternal; hell was that place "down there" fiery caverns where horned devils with pitchforks poke and prod the damned for eternity. Those images, those themes, are part of the popular religion, but they don't represent anything remotely like what Christianity--in all its many different denominations and traditions--has said over the last two millennia. And this isn't just a denominational thing, every mainstream Christian church, as part of its official confession of faith, teaches there is a future resurrection of the dead--Orthodox, Catholic, Lutheran, Anglican, Presbyterian, Methodist, Baptist, all of them.
And it's not like something like the resurrection of the dead is just a small little part of the Christian religion, it's at the very heart of the Christian religion, the quintessential confession of the Christian religion is that Jesus Christ was
raised from the dead. Resurrection isn't just something tacked on the side, it's the very core of the religion. In his first letter to the Corinthians St. Paul says that if the dead do not rise then Christ Himself isn't risen, but because Christ is risen we confidently believe the dead will rise on the last day. The one doesn't exist without the other; Christ is risen, and so we too shall rise; if there is no resurrection of the dead, then Christ Himself did not rise and Christianity is a completely worthless religion.
So very often there's a major divide that exists, between popular religion and Christian religion. What is popularly believed and what is actually confessed.
Indeed, I would say that if someone says they have heard the Christian message of the Gospel and they defined it as something like: "Jesus died for our sins, ask Him to forgive you, go to Heaven." Then they have about as robust an understanding of the Christian religion as someone saying of Islam, "Muhammad penned the Qur'an"; in that it's not entirely false, but it's seeing only one or two brush strokes of the painting at best and being misinformed at worst. (For example, Muhammad
didn't pen the Qur'an, his followers wrote down what Muhammad recalled as having been revealed to him, according to Islam Muhammad himself was illiterate.)
-CryptoLutheran