Here's my hypothesis: Obama told Syria the US would get involved if the Syrians resorted to chemical weapons. Syria did use at least one shell with chemicals in it on an attack on Homs. Maybe it was a mistake, who knows. So a price has to be paid by the Syrians. Voila, Israel attacks a chemical weapons manufacturing facility.
Two mortar shells explode in Golan Heights, no casualties or damage reported (Haaretz)
from the article: Why did Israel attack Syria now, and why did the Syrians admit it?