Conformity is adaptation to societal norms. The idea behind conformity is that it is more convenient is everyone follows the same standards, and that there is one optimal path that everyone should follow. However, a population is more robust against threats if it has diversity rather than conformity. The sickle cell gene would be a good example. If no one had the sickle cell mutation, the population would be that much more susceptible to malaria, but if everyone had that gene, people would all be susceptible to sickle cell anemia. So, it is just as well that some people have it and others do not.
It might be the same way with psychology. Suppose there is a scale of credulity ranging from 1 to 100, with 1 being extremely paranoid and 100 being extremely gullible. If everyone were at 50, then everyone would be susceptible to extremely persuasive arguments or, on the other hand, everyone would reject that which sounds extremely suspicious. But sometimes the extremely persuasive is wrong, and the extremely suspicious is right. In those sorts of situations, people on the tail of that bell curve will tend to survive and prevail, unless their fellow-citizens force upon them conformity.