Sorry it’s been a while and I was going from memory. It was more an opposing faction that simultaneously resigned than a separate party and I think they may have just told former donors to give directly to individual campaigns rather than the party.
Either way they’ve wrested control back already. If you would like to read more, here’s a couple articles about it
https://www.nevadaappeal.com/news/2021/mar/11/other-six-basin-states-know-colorado-river-droppin/ https://www.socialistalternative.org/2023/06/29/pulling-out-the-rug-what-happened-after-dsa-and-bernie-supporters-took-over-the-nevada-democratic-party/
I’m not sure how you expected me to glean any of that from “Huh?”.
In any case Mamdani has been in office less than a month and while he’s done some good I think you should wait a bit before you go calling him some kind of herald of democrat reform. They will likely continue to sabotage him while he’s in office because any successful socialist is a threat to their power and donors. It’s not like New York hasn’t had progressive mayors before.