So, in a big nutshell. (aka jump!)

[Dill]

Petraeus' security breech might have drawn criticism, sure. A lot of enlisted are angry that he got off so easy.  But NSC advisor doesn't require anyone's ok but the president's. I

But both Petraeus and Harward backed off because they could not control the composition of the NSC staff. Imagine being forced to keep a Fox News Commentator on board! Much less Bannon.

Either one looked to be very competent--much more so than high-flying, reckless, conspiracy-theorist Flynn.

This is not the only position in which the talent is hanging back. Few want to alight their career stars with a Trump administration which will inevitably fail.  No one wants to be in the position of Spicer, making statements that are outright lies because they are so ordered to.