Updated: Aug 17, 2021
I don't think it is a coincidence that some of the smartest people through time have included theologians. I'm the first to say being smart (or beautiful, or strong, or anything else) is as much in the eye of the beholder as in the beholdee, but I feel my point still stands.
And to me the reason is this; theology, as with science and spirituality, is a quest to understand ourselves and everyone around us. And it is the journey to do so in spite of (perhaps because of) the biases, superstitions, and gaps in knowledge, that cloud our thinking.
Therefore, saying the smartest people have included theologians (and scientists) is similar to saying the smartest people have been the ones that attempt to understand the world. Both by consciously looking inwards. and by seek this knowledge while accepting the search is never complete.