I can recall our sanctioning of Saddam sending oil to Jordan despite the sanctions. The USG made all kinds of exemptions for our allies in the region.
Whatever the motivation for shooting down the Russian plane, the Turks had called in the Russian ambassador in Ankara for two successive days prior to the shoot down warning about the consequences of their repeated violations of their airspace. From a Reuters news release prior to the downing of the plane.
NATO denounces Russian incursion into Turkish airspace
Erdogan is not a good guy. He is leading Turkey down the path of Islamic fundamentalism.
I read,can't recall where,that Erdogan had planned to take out a Russian plane simply to get pootie away from his massive smuggling operations. ISIS oil,drugs, human cargo,cotton, etc. you name it all going on underneath Russian planes. Not good for ol' Erdogan or his son Bilal and his family business interests.
As for the incursion Russsia claims they can prove they didn't go into Turkish air space.
Who do I believe? None of the lying bastards.