Assad had nothing to gain from mounting a chemical weapons attack on civilians. Quite the opposite. Just a few days ago the White House acknowledged that they were no longer trying to get rid of Assad, as Obama had tried to do. So in the face of that positive change would Assad suddenly do something to annoy the White House? Hardly.

On the other hand, hearing that the White House had stopped opposing Assad would be very bad news for the rebels in Idlib. Wouldn't it be useful to them if there were suddenly a big propaganda story they could use against the Syrian government?