My two cents fwiw (I’m 33), what I always heard growing up and what I’ve read/seen in docs is that it was a number of things that ushered in the new era of NYC. The biggest, was the takedown of the mob/mafia. They had their hands in everything seedy. Giuliani was one of the prosecutors and that’s how he made his name. Dinkins who was mayor at the time was beefing with the cops and unions to the point where they’d openly disrespect him. Giuliani came in and was a favorite with the blue lives crowd. Instituted a lot of broken windows policing tactics, ramped up quality of life summonses and tickets, heavy police influence and everything. This brought a lot of the yuppies in and made them comfortable. Every mayor since has added to the fukkery.
A small peeve that I have is people who complain about people who want the old NYC back. It’s not that people want the crime and chaos back, but they want to be able to live here comfortably. NYC has sold itself to out of towners and foreigners and shyt has gotten to the point where most families can’t live on one income anymore. The middle class has been getting squeezed out of here or are being forced to live in outskirt areas of the city. Many which become rich cultural locales until the blanquitos need somewhere to go and bring their rent hikes with them.