I agree with you. Smart people with dark traits become really good at painting their objectives in moral, altruistic terms. They tend to limit the display of their "dark traits" through actions to infrequent events where they stand to gain significantly and will suffer the least blowback.

This is because they understand that most people build trust by observing small actions. So the smart+dark personality combos follow the script until they can make a move where it really counts. And when they do pounce, they're good at subsequently coloring what they did through a kinder lens.

These people would be nearly impossible to pick out in a survey, because they make it their business to be impossible to pick out.