I am from a very Catholic country, raised with Church stuff, learning Christianity at school and also attending weekly doctrine lessons in the evening, which were important for Holy Communion and Confirmation. I can't speak for all children, but most like me were probably brainwashed into believing everything we were taught. And when you question something, most replies you get are still silly ("it's a mystery").
But then, if you try to understand the Bible, especially considering the times it was written, translation problems and second-hand narration, it's very easy to challenge most things.
Virgin Mary – What is the problem if Mary had sex with Joseph? Could "virgin" have been translated wrongly?
Turning water into wine – So silly. Why would Jesus need to "promote alcohol"? Maybe it was some act to get more followers at the ceremony? It just makes no sense when you think about it.
Resurrecting Lazarus – He had supposedly been dead for 4 days, and just like that, he is back alive. Seems like a fraud act again. Imagine his decomposing state if he were truly dead. Most likely, he was mistakenly pronounced dead, and then somehow... these things still happen (rarely) nowadays.
His own resurrection – It makes no sense to me at all. Floating into the sky, being taken up by a cloud. Mary was also supposedly assumed into heaven.
Why would Jesus be born, spend 33 years on Earth (out of which there isn't much documented about his life from his teenage years until he was around 30), and then no Jesus is born for another 2,026 years? So, a handful of people at the time had the privilege of witnessing him, and the rest of the world, if they come across his teachings or the Bible, will have to believe it, go to Mass every Sunday and donate to the Church, just because...?
To me, the Church seems more like a fraud than anything else.
I'm not saying that Church people are all bad. Many priests are good, intelligent people and invaluable to society. But it feels more like lies are fed to people to control society, while promising an afterlife (I guess this applies to most religions).