The Capitol demonstration devolved into a riot thanks mostly to the willful ignorance of the U.S. Capitol Police. The fact that demonstrators breeched the Capitol while Congress was meeting inside should always first and foremast be understood as an abject failure of law enforcement.
You clearly didn't watch the videos shown in the first day of the Jan 6th committee hearing. The capitol police were obviously overrun.
The Capitol Police should have never been in a position to have been overrun at the threshold of our Capitol.
Of course, an inconvenient truth of the Capitol riot is that there were/are many members of the USCP who were sympathetic to the rioters' cause, at least to the extent that they weren't going to employ lethal force to prevent them from entering the building.