What never seems to get asked is who came up with the video lie and why?
They knew it was an Islamic militant attack before they started the lie, so they knew it was a lie when they spread it.
Who and why needs to be answered.
The speed with which they trotted out the video lie suggests that they had knowledge of the video beforehand. That, in turn, suggests that they knew in advance that they might need a cover story for an attack that they knew might be forthcoming. And they still couldn't bring themselves to arrange to defend the place. Almost like they didn't want the place defended.