The idea of the missiles from the Russian perspective is not difficult to decipher. The Russians do not wish to prolong the war, they do not want the U.S. and its side-kick Israel to win the war by extending U.S. imperial power deeper into the ME. Historically, imperial powers inevitably hit a wall as they attempt to extend their aphere of influence and control.
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: U.S. warns Russian missiles may embolden Syria's Assad, prolong conflict