I think the thing that Chris Rabb and Janeese's victories show is that progressives who want to win in heavily Black cities need to independently develop or align with existing Black communal politicians and their infrastructure.
I also think both Mamdani and Janeese’s victories illustrate how trashing big-city “transplants” is an electoral dead end. In both DC and NYC, newer arrivals and longtime residents were on the same page. It was the wealthier white people who tried to divide this coalition that proved out of touch.