This is a hypothesis, without anything but the course of events to promote it.
That’s all about to change.
It all makes sense once you realize this is all a money deal. The Saudis/Qataris want to sell their natural gas to Europe, and run a gas pipeline to do it. They have to run it through Syria, and the Russians don’t want that because they currently have the monopoly on natural gas sales to Europe. The Iranians don’t want the Saudis to sell their gas to Europe. In fact, they want a competing pipeline run across Iraq and Syria to a port on the Mediterranean. The Saudis have used their petrodollars to bribe American policy makers into supporting their position. The Russians have used their long standing ties to the Assad regime to get Syria to oppose it. The Saudis ginned up the uprising against Assad to make a regime change, and get their pipeline. ISIS is in part a Saudi creation as part of this policy, but it seems to have become more virulent than its Saudi masters wanted.
The Turks originally backed the Saudis, as they would get money for transit rights and a cut of the gas. They have been backing the “rebels” in this confused brawl. However, with the victory of Donald Trump, they see that America will no longer be Saudi Arabia’s puppet in the Syrian policy. The intervention by Russia has militarily decisively tipped the scales in favor Assad, while Trump’s victory decisively tipped the diplomatic scales away from Saudi Arabia.
Thus, the Turks are at the table as realists, trying to salvage what they can from this deal since they are very uneasy neighbors of Russia, and now have very real reason to question America’s support of their position.
Gotta hand it to Putin in this situation. He was playing chess while 0bama was playing with himself.