Why did the Pentagon delay sending the National Guard to the Capitol riots?

Isn't it funny how they had the national guard for the march protesting against Mr. Floyd's murder dispatched and waiting before the march?  It is apparent, Trump held them back in hopes of stopping the certification of the electorate college votes.  He no longer has this authority so unless they bomb the capital I don't think they can do much damage today.  

Trump ignored help for the Capitol.

Until there's evidence otherwise it looks like the worst kind of bureaucratic delay.  Wishful thinking that police forces would be able to get it under control and a complete ignorance of what was actually going on.  A lot of mistakes were made, but things in retrospect always look more obvious then they may have been to the General at the time. 

People should not be having riots that cause violence and damage to property. 

Several days before the demonstration Trump had offered to send 10,000 National Guard and the Capitol Police turned down the offer.  Given the chain of command and the need to get troops ready it takes time.  Why did the Capitol police not accept the original offer?

Why didn't trump tell them to? Trump and his supporters wanted that call delayed.