According to Syrian reports, they had evacuated the sites three days ago. That’s an inevitable consequence of the delay in striking, but there were probably good reasons for it. In a sense, it’s an admission by the Syrians that these sites are part of their chemical weapons industry, that is an industry that they are not supposed to have.
Opponents of the strike often ask a legitimate question: why would Assad risk using chemical weapons in a war that he is already winning? But one could also ask: why would Assad, as hard pressed economically as he is, and already winning the war, invest scarce resources in the development and manufacture of chemical weapons if he wasn’t planning to use them?