From the linked article:
> New York's homicide count went up by nearly 40 percent with Mayor Bill de Blasio stating that the figures should worry all New Yorkers and it has to stop.
Numbers started to rise after this:
> The New York police commissioner announced on Monday that he was disbanding the Police Department’s anti-crime units: plainclothes teams that target violent crime and have been involved in some of the city’s most notorious police shootings. https://www.nytimes.com/2020/06/15/nyregion/nypd-plainclothe...
The other cities mentioned had similar decisions that seem to have backfired spectacularly.