The Russians and the US are in a trade war over who will supply oil and gas to Western Europe. Big Oil (Exxon, Shell, BGP, Valero, etc) want to supply Europe with gas and oil via tankers. The Russians can deliver fuel more efficiently with pipelines, Assad is a cruel butcher who murders doctors and nurses, and the US should in no way support him. I agree that the US has no serious interest in Ukraine EXCEPT THIS: if Ukraine decides to interrupt the oil and gas pipelines that cross its territory, Big Oil has an advantage.
\
I consider Putin and Big Oil to be equally rotten.
Russia wants to control Syria to prevent a pipeline across it from Qatar and the UAE to the Mediterranean coast, where tanker ships could load. Saudi Arabia's oil is also in the East, along the Persian Gulf.