No question that Putin is looking out for his own interests and not doing a charitable operation for the world. Propping up his puppet does help him control the Middle East though.
It is in Putin’s interest, not just regarding Syria, but all those restless former Soviet/Muslim elements on his southern flank. All those “stans”. I doubt that Egypt, Saudi Arabia, Jordan, or even Turkey are likely to jump into bed with him, and even with Syria stabilized in his favor, he doesn’t have all that much that is new. These guys will continue hating and fighting each other no matter what Putin or we do.