Police regularly stops huge mobs of people, there are units dedicated to that. What I still can't understand is why the police wasn't prepared for it. Isn't th

Police regularly stops huge mobs of people, there are units dedicated to that. What I still can't understand is why the police wasn't prepared for it. Isn't the FBI supposed to infiltrate dangerous groups? Or was the "march on capitol" completely unplanned before Trump suggested it? Finally, has nobody considered that something like this might have happened? (It was obvious to me, as well as at least one thinktank.)