Why have brilliant people failed at these before?

Maybe 2-naryish thinking about intentions in general is somehow useful. Maybe this has something to do with how we come up with new uses for things and spot other optimizer-thingies before they kill us. Maybe the brain makes new discoveries by confusing language with new meanings from time to time but unfortunately this can be a failure mode too.

Maybe it really is just a simple logical fallacy. The brain came up with the 2-nary grammatical shortcut, and didn't properly keep it separate from the original 3-nary concept.