Yep, it's an evolution of Al-Qaeda in Iraq (that's why all these people were in jail in first place), built under their noses [their = the US]. In English, that means it was hidden from the US, not complicity.

Now, if Assad and the Mullahs didn't support Al-Qaeda in Iraq in the first place, or if they got their Iraqi pawns to keep the lid after the US left, maybe the jihadists wouldn't have been strong enough to create ISIS later on.