I've been watching CNN to get some understanding of why police precense was neglible on January 6.
There seems to be some jurisdictional issues as the Capital Buildings are "protected" by Capital police. Other police jurisdictions cannot interfere with the Capital domain.
There will be an inquiry happening. I would not be surprised the Capital Police were told to conduct "business as usual", which was not enough for size and ire of the crowd. Who gave those orders? Hmmmmm.
Let the inquiry do its job before accusing the police of siding with the rioters.