There are three reasons. Don't expect Tom Friedman to come up with any of them, or to understand anything about anything. Ditto for Nicolas "Heart-On-My-Sleeve" Kristof, who is too busy reporting on how much he wants to help, and how much he wants you to know he wants to help, child prostitutes in Cambodia or the Congo, or the obvious wretched of the earth anywhere.

The three reasons:

1) Georgiy Arbatov is gone, but Russia, as the Soviet Union, has longstanding ties to Syria and its odious regime.

2) The Russian government doesn't like intervention because it might give various nationalities ideas about intervention in the country with the most time zones, and that would never do. 

3) Russia, not the Soviet Union, was the historic protector of Christians threatened by Muslims. In the past, it was the South Slavs, oppressed by the Ottoman Turks. But the Russians, with their Syrian experience, understand perfectly that if the Alawite regime goes, the position of Christians in Syria, including that of the hundreds of thousands of Assyrians and Chaldeans who fled Muslim attacks in Iraq and are now in Syria, will suffer, and so will the position of Christians everywhere in the Middle East. The Russians apparently know this better than, say, the louche quai-dorsayish Alain Juppe and the excitable Nicolas Sarkozy of France, once the historic protector of Christians in what are now Syria and Lebanon.

Most newspapers will mention Reason 1 or Reason 2, or 1 and 2.

None will Mention Reason 3.

But it's there.

And who do you think, back in 1914, in Russia,  wanted the Russians, as part of their war aims, to seize and annex Constantinople, a city which was then 50% Christian? 

Prof. Pavel Miliukov and the Kadets (Constitutional Democrats). The liberal, secular, anti-monarchist, advanced people of Russia.

That's who.