You are not the only one who believes that you are smarter than people actually think. Reason for this phenomenon is that you know yourself better than the rest of the world. You are not crazy, delusional or nuts.
The reason for this is that you have not expressed yourself enough to show others your true potential. How many times have you for example been the first to raise your hand for a question during a huge event? How many times have you been the first to volunteer for an assignment in a group or how many times have you approached a stranger you really liked, to start a conversation?
Chances are you have not been that! proactive.
Moral of the story here is that people should know about your existence in the first place before they can appreciate your skills or you as a person for that matter.
In any crowd, there are thousand others that equally match you pound for pound when it comes to brains, looks and all the rest. Your only advantage over them can be achieved by your behavior and attitude.
So from today onward, never wait for others to make the first step. Make sure that you are the one who leads. It is easier said than it’s done, yes. But it is the only way.