Mormons may also have some immunity the detrimental effect IQ on of fertility. In the general population increasing income (highly correlated with IQ) is associated with both declining fertility and declining religious commitment. In Mormons the reverse is true. Mormon fertility is positively correlated with income and Mormons with higher levels of formal education tend to be more religiously committed.
On multiple religious measures Mormons stand out for having exceptionally high levels of religious commitment. More than nine-in-ten Mormons report a belief in God and that the Bible is the word of God. Mormons are also very observant in their religious practices with more than eight-in-ten praying daily. Mormons strongly support a strict interpretation of their faith and the preservation of traditional beliefs and practices.
Are these demographic differences actually due to the Mormon religion? How can we be confident these are not just population level differences that happen to correlate with religion? To better answer that lets examine the Jews.
Didn't have a chance to digest it all yet, but what immediately pops out for me is that men may be (unconsciously) using religion to keep the women focus in child bearing which would not normally the case in a more liberated affluent society. I think you wrote before in the Economic Devastation thread about how society is a balance between preventing people from doing actions that opt-out and harm the collective well-being balanced against the society becoming too totalitarian and imploding.
So it seems religion forces all parties to subject their free-will such that the balance is maintained.
Religion also has failure modes though such as the Spanish Inquisition, although one might argue those are extreme cults that have not stabilized as the Jews apparently have over 1000s of years.
What high IQ people miss is apparently that God doesn't have to be a factual truth in order for religion to be an optimum strategy for society. Thus they aren't as high IQ as they think they are, haha.