As you may recall, Russia took its good old time to get directly involved in Syria. Even though Russia had been a forever backer of the Assad regime, Russia seemed reluctant to take decisive action. Apparently, after years of assessment, Russia decided that ISIS/ISIL or Daesh, whatever is your choice of what to call them, amounts to a much greater evil than is the Assad regime in Syria. Apparently also, Russia assessed the moderate opposition to both Daesh and Assad to be unreliable, disunited, and too weak to be effective. And, finally, Russia seemed to be somewhat indifferent to the Kurds in Syria, even though the Kurds had proved to be effective fighters against both Daesh and Assad.
In recent months, Russia has given full air support to the Assad regime. This has included, at times, attacking both moderate opposition forces, and Kurdish positions. The Russians are "all in," in the modern parlance of Texas Hold 'Em poker! And Assad's army has proved that the Russians, by supporting the Assad regime strongly, made the best choice in order to defeat Daesh. Now, many Americans, and innumerable Syrians and others in the Middle East, are appalled that Russia is propping up a man, in Assad, who has committed terrible atrocities against his own people. However, I am drawn back to the comment by Winston Churchill when he was questioned about his government's mutual defense agreement with Joseph Stalin against Adolf Hitler after Hitler's armies had invaded Russia. His answer was, "If Hitler invaded Hell, I would make at least a favourable reference to the devil in the House of Commons."
Bashar al-Assad is evil. Russia has chosen to support what they consider to be the lesser evil. Let's hope they do not come to rue this decision some time in the future.