It's not that hard. Trump, a narcissistic bully, is afraid of people who aren't afraid of him. Mandami isn’t afraid of him.
People talk about sick burns and smackdowns and all the rest. But man, Mamdani's biggest flex and power move has always been Trump's docile and friendly-puppy-like behavior in Mamdani's presence. Like EVERY TIME. It's like someone flips an electrode in Trump's brain and puts him into docile mode.