Manipulating and tricking people isn't easy; one reason why is because there is no guarantee that the target of manipulation or trickery will fall for it. Even if the target of manipulation is stupid, naive, or gullible, and the target is intelligent there is always the possibility that the target of manipulation will see through it and catch the would-be manipulator off-guard.

The reason why someone might underestimate another's intelligence can vary; perhaps the manipulator looks down on the manipulated party for one reason or another and assumes them to be easily tricked; for example, an old person might assume that a younger person is easily manipulated because of their lack of experience. Someone who's skilled at manipulating others might get cocky and assume that they no one can see through them, and end up being caught off guard when someone they tried to dupe sees through them.