I searched a bit, the main thing I can find is that 7 days ago, Mamdani appeared on stage at an event in Staten Island, where he only got 23% of the vote. Multiple (at least 4) people booed him, and he left the podium/stage after roughly a minute during which he thanked various people.

So… He went to a borough where he wasn’t very popular, and he still isn’t very popular there, I guess? This is just like the ending of my own relationship’s honeymoon phase, when my sister in law that has never liked me, still didn’t like me after I got married.