While Russia's goals are very clear - to maintain status quo - simply put, Assad may be not the best guy in the World, but there is no viable, or even more or less sane alternative in sight. US interest, or at least US officially stated interest is to topple Assad regardless of who comes instead of him. What is the rational for this? A hope that after the dust setles some religious fanatics will be more reasonable than other religious fanatics, or what? One should not look very far to find examples where it goes badly. Yet US stubburnly pursuing this apploach one country after another after another.