Is blind faith an indication of low IQ or indoctrination at young age or could there be another reason?

I was born in a communist country and I wasn’t exposed to religion until I was 14. Until then I’d never even heard of Jesus, Mohammad, Moses or any other religious figures. Then in early 90’s democracy came along and religions sprung like mushrooms after rain. Being an academic and curious child I read the Bible, Koran, Torah, Talmud, Buddha, Confucius, etc. but I found it incredibly hard to believe in any of them. There’s so much utter nonsense in those books that had me thinking surely anyone with an ounce of brain couldn’t possibly believe these tales. But apparently over 7 billion people do. How is this possible? Surely it’s indoctrination from an early age and low IQ. Can anyone offer another explanation?

Is blind faith an indication of low IQ or indoctrination at young age or could there be another reason?
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