Then how come we have so many? Most who do not have an elevated (sorry ill correct myself, ambititious) sense of intelligence, will stick with the most convenient religion. Which is why we have hypocrites and complete imbeciles. Religion and science are both the studies into finding the truth, but both can be severely dumbed down to the convenience level of a bubble gum sorority brat.
Tl;dr, stupid question, yes its completely related to it
Children born into families that are religious are inculcated into the religion by their parents ... Brainwashed from a very early age. Eventually they can't discern what is rational, sensible and of course, if their parents say something is true, they believe it. Children can be very intelligent, but gullible.
There are geniuses and idiots in every religion, so I doubt intelligence has much of anything to do with why people subscribe to one religion rather than another. I think the primary reason people adopt the religions they do is because of the environment they grew up in and what they were exposed to. It could be that intelligence explains why some people change their religion. Although some people change religion because of who they're dating or out of rebellion against their family or because of being exposed to something new or for convenience or whatever, there are a handful of people who change religions because they were intelligent and looked into it. But even then, intelligence doesn't dictate religious choice because people convert to and from every different religion.