I remember a political cartoon from the '80s that had a boardgame-style spinner with "Send Troops to" written across the top and in the pie wedges, "Grenada" "Beirut" "El Salvador" and a few other countries. It was captioned "Reagan's Policy Distraction Device" or something like that. Putin is in Syria because ISIS is a great distraction for the west, and because he can look tough without having to do much, and because he's got a policy spinner of his own to deal with his domestic economy issues. I'm skeptical that the Russians have any long-term intentions in Syria; other than getting the West bogged down in the Middle East and a short-term distraction from domestic affairs, there's little upside to their presence. I guess Lindsay Graham is ready to march. Not personally, of course. Other people's kids, as per usual.
Fighting in the Middle East also allows Putin to stage heavy military presence in his illegally overtaken lands in the Crimea and Chechnya. "Eets zo much eezier, and much shorter of flight, to get to Syria from bases in glorious new Russian republicstans!"