Fair comment, mate but this has been ramping up for months. With that many people protesting the electoral vote I'd have expected to see far more LE around than there was. Private security around the nation have been taking steps to bolster security at their installations, and have been telegraphing the potential threat since late September. As the rhetoric from the WH increased, I have a hard time believing that Capitol police would have been that naive.
Granted I wouldn't have expected the full stormtrooper outfit but for protestors to be able to enter while it was in session... That is