This article appears to offer an excellent summary of the new geopolitical situation in the Middle East following the defeat of ISIS which was originally promoted primarily by Saudi Arabia, the US, Turkey, Qatar, and Israel to produce regime change in Syria. The Russian involvement in backing the Syrian government proved a crucial factor that tipped the scales (def.) that has ended in a very different geopolitical scene.
The result of the war in Syria has carved out a new Middle East, where the likes of Riyadh, Tel Aviv and Washington, previously regional masters of all they surveyed, appear to have more or less been deliberately cut off from the decision-making process. While it can be argued that Washington has played out its role in the region with the defeat of Daesh, thanks to Trump's "America first" policies that resists direct involvement in conflicts, Riyadh and Tel Aviv do not seem to have any intention of accepting Tehran’s new role in the region, even as it is supported by Turkish and Russian diplomacy and even military might.
The aggression against the Syrian state initially saw a compact front comprising the United States, Saudi Arabia, Turkey, Qatar, Jordan, Israel, France and the United Kingdom. All were at the forefront of arming, training, financing, assisting and treating the injured of the tens of thousands of terrorists sent to Syria. It was a destabilization operation with few precedents in history.