A lot of beliefs are cultural and not directly related to intelligence. From an outsider's perspective, it can be difficult to tell which beliefs are merely fact-based and which are rooted in culture.

I think an important thought experiment here would be to really imagine people going to war, killing each other over whether or not biblical transubstantiation is literal or metaphorical. who had the "intelligent" belief in this case? I'd argue neither side and that this was pure tribalism.