Who & what are the demons ?

Too funny. It seems that they also stop telling the truth.

which brings up a fair question. Does everyone automatically start out as an atheist or is that something requiring mindful decisions?

Who are "they"? And why do you make this assertion? Are you claiming that Fundamentalists lie more often than the general population?If so, is your reasoning that they know and yet deny reality?You yourself have said that some of your own beliefs are irrational.

No idea of how they compare to some general population but yes, I believe that Fundamentalist Christianity is based on lying and wilful delusion. Know? No. I doubt they even understand what the word "know" means. Absolutely. But I try hard to not confuse "know" and "believe".

Do you really need to ask that?You think a child would know and understand the religious stories without being taught them almost from birth? It's not a coincidence that you're a Christian but it is an accident of birth. To have been a believer of any other religion you would have had to have been born to different parents, often in a different country.There are exceptions where people swop religions later in life but there are NO cases of people spontaneously becoming Christians or any other religion without having first learnt of it.Religiosity is learnt behaviour.

I would argue that atheism is also a learned behavior. Of course children are told stories. They also have to be taught what is truth and what is myth.

Why don't you try arguing it? So children are taught the stories of Jehovah or Allah or Jesus and become Jews, Muslims and Christians.Imagine a world where children are not taught the stories. How do they become believers? They can't spontaneously believe in something they know nothing about.There wouldn't even be a word for what they are would there? They've not learned to be atheist because there's nothing there to not believe in.Given that we have these stories in the world, do people learn to become atheist? No - they mostly have to unlearn belief. But in countries where atheism is the norm, they at least start life without the burden of belief imposed on them and as they learn more about the world they can accept a belief or not as a choice instead of an imposition.

The same way that the first believers came about and the first religions emerged. Weird shit happens and people talk to each other about it.It turns out that people do find personal religions on their own without having beliefs dictated to them.

Oh sure, you mean like Mormons, Scientology, Wicca etc.Yup, people just can't help making stuff up, then worshopping it. Some people seek power and more people are gullible. Luckily it's in decline.

So they can start believing something they knew nothing about?You're contradicting yourself.

Now you're being disingenous.The leaders make the stuff up, the followers worship it.
(And, donate their money of course.)

And that is just one of the ways in which people become religious - there are others too that you're failing to consider, or worse, just outright denying.

That's the way all the major religions have started and developed so..... Before I can deny them, you have to tell me what they are.

So people can still be religious even if membership in major religions declines.

Since there's a strong correlation with the local religion - children in North America don't spontaneously start believing in Odin or Ganesha - so it definitely seems to be learned behaviour. I suppose it's possible that they have an innate belief in "something" like gods or leprechauns and that innate belief might be imprinted with the local religion.