And the senate floor isn't a particularly important piece of ground to hold (when the Senators are not there at least).
Expending lots of resources and good will smashing what was essentially theatre-- wouldn't have been a good move.
If only we treated more protests like that: Stood back and people show their anger, then move on with our lives -- message heard-- with minimal injury and damage.
[I'm aware that a protester was shot and killed inside the capitol building -- but relative the scope of the event, I think it's still fair to characterize it as that way]
FWIW, the Capitol building is normally substantially open to the public.