It seems, then, that the goal is to motivate (and hence emotionally reward) diligence and intelligence.

It occurs to me that explaining things to people who "don't get it" is often actually a matter of them not wanting to get it - but being polite enough to feign interest (even to themselves) all the way through the conversation. Most likely, their "wanting to get it" is a "belief in belief" - it's part of their identity and personal integrity that they wish to listen to evidence, but in reality their emotional brain is sending out "what is the point of paying attention to any of this gibberish?" signals, and so they let their mind drift off to other things while they "try" to follow along. They likely do not even realize they are doing this.

This is consistent with my own anecdata, which is that engaging people emotionally before you start explaining something to them, and genuinely praising them - without being condescending - each time they reach a milestone along the path towards understanding your explanation, tends to have a much higher chance of succeeding in them "grasping" the explanation and actually attempting to incorporate it into their world-view.

The problem I'm currently working on, is that when they do attempt to incorporate it, if it winds up causing cognitive dissonance with something else that's already in their world-view, they will often become irrationally hostile to me for having "slipped in" an "enemy soldier".