You might find this of some interest: [nature.com]

Religious belief is not caused by "inferior rational abilities" although they certainly can be helpful. Indeed -- there are many varieties of religious belief, some exponentially more irrational than others. So as an unqualified statement, I can't agree with you.

I don't know how many brilliant people regress to religious ideation or whether they tend to do so more late in life. I haven't seen any indication of that personally. What have you seen? Do you have any citations?

Intelligence is just potential, it says nothing about whether the potential to think effectively is actually realized, or isn't counteracted by other things. I have a fairly high IQ but used to be an evangelical Christian. I don't think my intellectual capacity spared me my childhood religion, or was the main impetus to get out of it. It probably was mildly helpful in the process of getting out, I suppose, but I think that would have happened anyway. In point of fact I would say that my intellect has been a lot less helpful in most areas of life than people tend to think it would be.

Think of intelligence like a fast CPU. Think of smart religious people as people with fast CPUs running crappy software.

I think it is the fear of oblivion that makes people want to hope in an afterlife.

When I was 20 I recall having a conversation with my 40 something boss. He asked about my beliefs and I was straight with him. He asked if I feared death. I did not, I was twenty, death was the furthest thing from my mind. I asked why he wanted to know. His reply was that if I didn't believe in an after-life did the thought of ceasing to exist scare me? It's nothing, why is that scary? Furthermore, if I'm right, I won't know. I explained that the nothingness of before I was born wasn't scary so why should the nothingness of after I'm gone scare me?

I'm now older and don't like the fact that my knowledge will be lost. That everything I've learned over the years is seemingly for nothing if indeed there is nothing after this. I can certainly understand why the human condition, upon nearing death, is comforted by the idea of a heaven.

Rationality is good of course, but only as good as the accuracy and completeness of the data you apply it to. It can take a long time to accumulate enough knowledge to understand that “religion” is not just “another form of superstition” for all adherents, even if it is for most.