The thing to remember is Mamdani's success isn't just him being such a great guy. Sure he's nice and charismatic, but he wouldn't be possible without the massive grassroots organizing that got him elected. He couldn't be pumping out these policy wins without the support of a great cabinet of passionate people lending their expertise to make all this happen.
It might be hard to replicate Mamdani's raw charisma, but we can and must replicate that movement for any office we hope to achieve. It is harder to do this on a national level though, but we already almost did it with Bernie, and the movement's only grown since then.