Aetheism is a product of low environmental exposure and lack of cultural diversity.

Suggestive. From The Origins of Religious Disbelief: A Dual Inheritance Approach by Will Gervais, Maxine Najle, Sarah Schiavone, and Nava Caluori. From the Abstract:

Religion is a core feature of human nature, yet a comprehensive evolutionary approach to religion must account for religious disbelief. Despite potentially drastic over-reporting of religiosity[1], a third of the world’s 7+ billion human inhabitants may actually be atheists—merely people who do not believe in God or gods. The origins of disbelief thus present a key testing ground for theories of religion. Here, we evaluate the predictions of three prominent theoretical approaches to the origins of disbelief, and find considerable support for dual inheritance (gene-culture coevolution) approach. This dual inheritance model[2,3] derives from distinct literatures addressing the putative 1) core social cognitive faculties that enable mental representation of gods[4–7], 2) the challenges to existential security that motivate people to treat some god candidates as real and strategically important[8,9], 3) evolved cultural learning processes that influence which god candidates naïve learners treat as real rather than imaginary[3,10–12], and4) the intuitive processes that sustain belief in gods[13–15] and the cognitive reflection that may sometimes undermine it[16–18]. We explore the varied origins of religious disbelief by analyzing these pathways simultaneously in a large nationally representative (USA, N= 1417) dataset with preregistered analyses. Combined, we find that witnessing fewer credible cultural cues of religious commitment is the most potent predictor of religious disbelief, β=0.28, followed distantly by reflective cognitive style, β= 0.13, and less advanced mentalizing, β= 0.05. Low cultural exposure to faith predicted about 90% higher odds of atheism than did peak cognitive reflection. Further, cognitive reflection predicted reduced religious belief only among individuals who witness relatively fewer credible contextual cues of faith in others. This work empirically unites four distinct literatures addressing the origins of religious disbelief, highlights the utility of considering both evolved intuitions and cultural evolutionary processes in religious transmission, emphasizes the dual roles of content- and context-biased social learning[19], and sheds light on the shared psychological mechanisms that underpin both religious belief and disbelief.

Stripping away the academic jargon and verbiage, it appears that this research suggests that atheism arises as a consequence of reduced religiosity in the subject's environment. Further it concludes that cognitive reflection had relatively little contribution to the probability of atheism.

Makes logical sense. Whether it is true or not awaits replication. I think there are good reasons to treat this as less than robust evidence for the time being. However, accepting the findings at face value, it does suggest that those lamenting a decline in social values (decline in religious observance and rise in atheism) are in part contributors to that decline by hiding their own religiosity. It also suggests that electing atheism is far less a reasoned and logical conclusion reached through high IQ thinking and much more simply a product of lack of environmental exposure.

Or at least that is one way to interpret the findings.