Recently a rioting group of protestors attacked congress after attending a presidential speech. The members from both parties and the senate narrowly escaped. One capitol policeman and one protestor were killed. After being evacuated to a bunker, the leadership of both parties phoned, at least, the following bodies: the Department of Defense (DoD), the governor of Maryland, the governor of Virginia, and the Department of Justice (a few other minor dept.'s as well).
The DoD's response was far slower than the other actors. The actual DoD guard deployment time was four hours, hard to judge the quality of that. Seems slow but gathering, arming and deploying is tough. More damning, the Virginia and Maryland guard offered to enter at 3:29 and received authorization at 5:45. The Maryland National guard waited at the border for 1.5 hours to receive authorization. That means the state of Maryland had time to decide, convene their leadership, gather their troops and drive them to the DC border, then watch two Game of Thrones episodes before getting a phone call from the DoD. This looks very embarrassing for the DoD.
Meanwhile there are rumors that President Trump intentionally delayed the DoD response. There's also a rumor that VP Pence authorized the deployment and Donald was not consulted the entire day. In their Wednesday briefing Sec of Def Miller did not mention Trump, saying he "spoke separately with the Vice President [Mike Pence] and with Speaker Pelosi, Leader McConnell, Senator Schumer and Representative Hoyer about the situation at the U.S. Capitol."
So far the DoD has deflected blame onto the Capital Police (CP) and DC Mayor Bowser. This might explain the lack of preparation, but it can't explain the slow response. The national guard story in particular has no explanation. AFAICT, their options are to tell congress "we were incompetent" or "Trump did it".
I expect the DoD will place the blame for this episode squarely on President Trump. I predict that at least one named official will state either Trump declined to call in the guard immediately or that they knew not to ask. Prediction is true if an official resigns (post Jan. 7) then makes the statement, but not if the statement is anonymous. Must occur before March 1st or the first congressional hearings post-Trump, whichever comes first.
Probability = 80%
Congress sets the DoD's budget. If they plead incompetence, they risk their budget getting slashed. Shitting on the old president does make the agency less trustworthy to future presidents, but I expect the budget concerns are stronger. Also blaming Trump is accurate, comparing Maryland's response time to Trump's.
Why might I be wrong
Schumer, Pelosi, McConnell and Hoyer were on the phone with DoD at the time. In t he unlikely event that incompetence is true, the Congress might already know.
The DoD has enough leverage to survive. The DoD is sort of a monopsony, hard to replace for congress.
Commander in Chief legal bullshit. Maybe it'd be unconstitutional to admit they called Pence not Trump, even if true.