Religion is not about intelligence, and it's not actually about "belief". Religion is more like an optical illusion; your brain tells you something is true when it's actually not.
Scientific study tells us that our brain pre-processes the world before we are even aware of it. For example, your light-sensitive retinas have a non-sensitive spot, a dumb design, which causes a "hole" in your vision. Your brain pre-processing feeds you a picture with the hole mended so convincingly that you are never aware of it. But sometimes, there is an error in the pre-processing, and your brain feeds you a lie while telling you it's the truth. That's why everybody else is superstitious except you.
You don't have to "believe" in an optical illusion. Your brain simply feeds you the wrong information. Smart people are just as fooled as dumb people. Religious belief works the same way. It is such a completely convincing lie, because the brain itself is actually fooled, in the subconscious. Their brain tells them it's real, but it's not. It's no more stupid to be religious than it is to be fooled by an optical illusion.
We are all susceptible to false connections, superstitions and illusions, just like religious people. Me personally, I feel bad for them, and cut them some slack. You?
P.S. Think you're too smart to be fooled? Well, it turns out the illustration I got off the internet was made wrong. The top line really is longer. Did you believe they were the same length because of the caption? We can all be fooled into believing false things are true.