Said idiot mayors don't just fall into office at random. They're voted in by the majority of the electorate. The problem with NYC isn't jackass Adams it's the New York morons who voted for him
New York City voter turnout is usually below 30% of those who even bothered to register. Knowing they don't purge the voter rolls, the percentage is likely below 20% but they don't want that truth out there.
No one bothers to vote in the general election in such blue cities. The United States doesn't have a legitimate candidate voting system; at best voters choose the lesser of two evils. We really need "none of the above" selection added to force political parties to find someone half decent.