So then why would people pack up and leave?

Heh.
Having lived through how fast an ineffective, weak mayor can piledrive a city, I'm here to tell you that Mayors can have a huge negative influence on the places they run.

Cops get votes. As in, if they don't feel like Hizzoner has their backs, you'll see retirements shoot through the roof and officers transferring to other departments as more of them say "I don't need this sh1t".

Then there's basic city services. Mayors control all that. Inevitably this guy is going to decide that things the city used to do they're not going to do any more...things like cleaning up graffiti and policing homeless.

Yeah, I've got my popcorn ready. I watched Seattle go from one of the greatest places in the entire country down to "Holy crap, wtf is going on here?" in the span of something like 6 months. Here's hoping NYC doesn't learn the hard way.