The assertion is, the "rebels" who have been previously caught transporting chemical weapons, who works closely with groups like Al-Qaeda, who have a habit of using civilians as human shields, stored their chemical stockpile in their compound in a civilian area, weapons which exploded after their compound was struck

Shocking, I know, it's clearly a conspiracy, we all know Al-Qaeda and ISIS loves civilians and have no interest in manufacturing an excuse for missile attack on their opponents

Whereas everyone knows the side that has air support and have troops fighting on the ground just thought one day: hey why don't we use chemical weapons on that building, for no tactical or strategic reason other than the lols, 

Yeah that must be it.... 
And Al-Nursa isn't Al-Qaeda, because it's spelled "Al-Nursa", duh.