A hypothesis regarding why Assad may have used chemical weapons, since everyone is baffled at the stupidity of the strikes:
"The purpose of this past attack, apparently, was to shock and awe and demoralize the civilian population and the regime to the point where they give up. It does not have great military value, but it is literally a mass-terror weapon, designed to basically overwhelm and demoralize the opposition."
Why Did Syria Still Have Chemical Weapons?
"...such extreme tactics aimed to demonstrate the government’s impunity and to demoralize its foes."
https://www.nytimes.com/2017/04/06/...bashar-al-assad-russia-sarin-attack.html?_r=0
The above seems reasonable. It may be the case that Assad grew impatient and simply made a bad judgement call.