one of many balls that were dropped: no formal FBI/DHS threat assessment produced

davesaddiction

A good read to help explain why there wasn't better preparation at the Capitol:

https://www.npr.org/2021/01/13/956359496/why-didnt-the-fbi-and-dhs-produce-a-threat-report-ahead-of-the-capitol-insurrect

Hard to imagine that this doesn't have something to do with bias, but clearly, Trump's tweets and words just prior to the march over the Capitol helped encourage many to take actual action.

Also, this:

Sund says he requested assistance six times ahead of and during the attack on the Capitol. Each of those requests was denied or delayed, he says.

Washington, D.C., Mayor Muriel Bowser also wanted a light police presence at the Capitol. She reportedly wanted to avoid a similar scenario as last summer, when federal forces responded to demonstrators opposed to police abuses who assembled near the White House.

https://www.npr.org/2021/01/11/955548910/ex-capitol-police-chief-rebuffs-claims-national-guard-was-never-called-during-ri

Too many worried about the "optics" of having the National Guard there ended up putting so many at risk, and resulted in the deaths of 6...