Yes, he’s young (34), yes, he’s Muslim (still a mystery to me why this is such a big deal), and yes, he beat out the establishment. Regardless of your political stripes, this New York City mayoral win is worth studying from a leadership perspective because it’s a transformational change masterclass. How did Mamdani move people to volunteer, fundraise and vote for him as the “anti-establishment” candidate?

“The more closed your network, the more you hear the same ideas over and again, reaffirming what you already believe, while the more open...