@bluemoon

One of those things of which libertarians often crow is 'a rising tide lifts all boats', so often interpreted as the general quantity of wealth entering a locale as a net positive. A moment's reflection proves that interpretation false: a billionaire moving into an impoverished community (she says with bitter irony) is unlikely to result in substantial gains to that community as a whole.

In contrast, a comparatively meager benefit increase to mixed communities, a rise in the base standard of living, carries all the benefits you've stated and more. It lowers crime, both actual and perceived (a person with options available to them will typically not pick the most dangerous), it allows use of public resources rather than leaving them to collect dust, and it instills a sense that it's better to be there, helping to stem the outflow which historically plagues disadvantaged communities.

In his support of free buses and other bonuses to those living in the city, Mamdani distinguishes himself -- rather than a New York Mayor, he's working hard to show himself to be the Mayor of New York.