Phil Giraldi, a former intelligence official, believes that it was a conventional attack on a warehouse which stored some sort of chemical weapons.
I ask again - why would the Syrian Government need to resort to weapons of desperation? They are winning and will win unless the US stops them.
Trump is caving in to the McCains to take the pressure off himself from the howling media and establishment.
For every Phil Giraldi you'll be able to find a different opinion.
As for your question, who knows what local operational developments might have prompted such an attack by the regime?
The only thing we know is that we don't know very much. Fog of war, innit? What we might suspect is that there are chaps sitting in the Pentagon peering at great big screens who know much more than we do.
In this day and age it's not a huge ask for them to see that X number of Mig-29s took off from the exact airbase that was neutralised last night in the moments before the chemical attack that took place. I would suggest that it would be a remarkable coincidence that those Migs followed a flight-path very close to the locations where chemical weapons were used at the exact time that they were used. The US have all of that airspace covered with very advanced radar systems considering their on-going operations in the area.