When NYC put 7000 police officers on extra duty, put up barricades, but the Trumpsters failed to show up. The made for TV, staged fiasco of 100,000 snarling Trump fans crashing police barricades wasn't going to happen.
The optics of no one showing up for the event would be even worse.
The whole game is to make people afraid to protest. And if they do protest, to frame them for crimes and delegitimize the protested issue.
It is a "head I win, tails you lose" setup.