This is sending a message to Assad you want us to keep out of your business and let you keep killing Syrians without any trouble from us you keep Hezbollah on your side of the fence. Don't drag us into this because you will loose and it will mean your downfall. Assad will of course talk tough in public but he cannot afford Israel getting involved because even without the civil war he would loose but with the war going on he needs every gun and soldier fighting rebels he cannot afford for them to go get killed fighting a loosing battle with Israel so things like air strikes from Israel sends Assad a warning without actually having to get involved.. The only country Israel needs to seriously worry about right now is Iran.
Shaffir to Herzog: Opposition failed to show leadership in political battles against PM (Haaretz)
from the article: With Syria strikes, Israel sending message to Assad: Rein in Hezbollah