some people say it felt so real they believe science is incorrect in saying that it is only a faulty brain?
An oxygen deprived brain is faulty. Why take the word of someone with a faulty brain over that of the scientific explanation?
The greater question here is not about what a person experiences when his brain is about to die from lack of oxygen. Rather it is about the psycho/social dynamic that draws people to make wild assertions about things beyond the reach of their knowledge base.
First people are drawn to mystical thinking. It doesn't have to be wrapped around Christianity. Even people in the west are mesmerized by eastern religions which they know nothing about accept that Hollywood likes to draw on their appeal. Did you see Dr. Strange, who get's in touch with personal abilities beyond our imaginations? The thought from a comic book, is highly appealing, and pulls you in.
Second, people want to believe in Heaven so they search for a confirmation bias to prove that it's real. Now how do you get to Heaven? You have to die right? Someone claims to have come back from the dead, probably egged on by his doctor because everyone gets a thrill from telling people he came back from the dead, and he claims to have seen exactly what you want dead people to see. Dying and Heaven are already wrapped together, so people gravitate to tales of oxygen deprived brains that died and went to Heaven, and then came back. The only way to get to Heaven is to have a death experience. The problem is that by definition, a near death experience is not a death experience. But you say, "Well, the person was kinda dead!" Sorry, not close enough, because he was never not alive.
Third, humans are gullible by nature. Humans are drawn to all sorts of things they have no way of verifying as true, they buy diet pills, vote for Donald Trump, by useless products all because someone lied to them, and convinced them of a reality that doesn't exist.
