> Religious upbringing or being indoctrinated into not thinking for yourself

This is a pretty strange claim to me. I definitely agree there are some religious strands that are anti-intellectual. But then there are Augustine, Ambrose, Thomas Aquinas, John Calvin, Francis Turretin, John Owen, etc., whose works most people are simply incapable of grasping, and fewer still can equal. Many of us are trained with these intellectual giants to show us not what, but how, to think.

Are you aware of these great thinkers and their contributions to your thought life?

To pick a random example among many, our concept of personhood relies heavily on a theologian named Turtullian, before whom person (Latin, "persona") merely meant an actor's mask (i.e, the role one plays). Tertullian explored the enduring "substance" of a person, regardless of what role they play in life -- concepts we now assume as a given, but were hotly contested at the time.

People are still intelligent creatures after all. It doesn't surprise me that eventually over hundreds or thousands of years people managed to have some critical thoughts.

Agree, but your previous claim was stronger than that -- that religious upbringing causes people not to think for themselves, which isn't an accurate claim. Critically, in the example I used, Tertullian's expression of personhood was explicitly counter-cultural, i.e., only something an independent thinker would come up with.