It’s not ‘his’ city. The President is the President of the United States.
Mayors come down the list from the President.
The people are to be protected. If the Mayor won’t do it well then the responsibility moves up the chain of command.
“Mayors come down the list from the President.“
The President has no law enforcement authority in any state without declaring a state of insurrection or rebellion (or invasion).
That he does not do so is incomprehensible.