The types of applied stupidity that are consistently profitable for the collective tend to open a multitude of big doors while closing a handful of small ones. The problem is that the environment isn't static. Meanwhile, rationality is the complement of stupidity.
Individuals are constantly learning truths they're willing to die for, while collectives learn which truths to reject for the sake of living longer. Being dumb is a herd immunity. Reciprocating stupidity has isomorphism with evolutionary process in general somehow.