Follow the money. Iran has signed contracts for $20 billion in weapons purchases from the Russians. A lot of that, or all, will be coming from the $150 billion that Obama is releasing because of the fake nuclear control agreement with Iran. So it could be said that Obama is funding both the Iranian and Russian military actions.
I think your post 24 is a real possibility. Of course we cannot know for sure, but it certainly makes sense. In another way we pushed this forward by sanctioning Russia and isolating them, driving them closer to China, Iran, Assad, etc...and to viewing the U.S as their enemy (again). Also by ignoring their worries about the expansion of NATO. All of that, plus the Iran deal, plus trying to oust Assad, plus withdrawing from Iraq and Afghanistan, ....
Everything we have done has pushed this event forward. On purpose? Some say yes. I say no. It has been out of ineptness and liberal ideological stupidity.