Having been a sw PM for 20yrs I think self-awareness and willingness to explain highlight those that are truly brilliant. They recognize their abilities and become accustomed to explaining their ideas. Your awareness of your own limitations is credit to your intelligence IMO. Others who get frustrated when having to explain or posture do so from posturing or insecurity. Being in a new position requires computation of many more inputs than a old timer too, slowing down thought by an order of magnitude. Who knows, you may be the smartest dude in the room. Good luck!