Intelligence and stupidity are opposites so one cannot lead to the other.
Religion, especially if it is false, is an absolutely genius concept. Many psychologists in the past have argued that humans only had the capacity to invent such a genius code of morals and purpose because the human has trouble committing any actions without an absolute purpose.
Your theory about the failings of intelligence is quite ridiculous; how would life be relatively at peace if we had animalistic minds? The human, without sharp teeth or massive power, would live in fear of other beasts constantly without foods. Many of us would die as children because of our lack to protect ourselves. I don't think many would appreciate that lifestyle, hiding in the tree from the incoming tiger, compared to sitting in a hotel suite 50 stories off the ground surrounded by other civilized humans...
Because we are intelligent, we are actually destroying ourselves, other lifeforms, and Earth. Without intelligence, drugs, guns, nukes, pollution, money, etc. wouldn't exist.
You say people don't do things without purpose. You are correct. The problem is, greed, hate, jealousy, prejudice, are all purposes as well. Look at religion today. There are so many corrupt priests and people who do it for fame and fortune. And the number of Atheists and religion abusers are always increasing.
You say life wouldn't be at peace if we were more primitive. Life as nature intended isn't supposed to be all happy, sitting inside a skyscraper sipping champagne. It's all about survival of the fittest, and the circle of life that recycles everything. Furthermore, you're only at peace because you live in a first-world country. What if you lived in Africa, North Korea, Middle East?
That's what modern society had done to you, and other first-world inhabitants. You can't imagine life without your comfortable surroundings. You say humans can't defend for themselves without modern inventions. How do you think the cavemen and the predecessors survived? By praying to their gods?
Granted, human intelligence has unstoppable progress. But it doesn't necessarily help in the long run.
This is only my viewpoint, not what I support.
I like this modern-day society, only because pleasure is so easily attainable. And I could care less if humans are destroying themselves. I'm a Nihilist.