[misiti3780]

I have heard two theories that seemed plausible to me:

1. The Capitol police are used to dealing with large protests. They happen frequently in DC, especially in and around the capitol. So they may have unfortunately assumed that there is no reason to think this protest would be different, and thus not prepared properly

2. They assumed that a pro-Trump, QANON crowd would be pro-police. This is probably not a bad assumption, some of the people were waving blue lives matter flags etc. If they assumed that, they might have assumed that they would not break the law and were under-prepared.

Another plausible explanation could be large portion of the officers were sympathetic to the cause, but I'm not sure I have seen any evidence of that yet.