As an example -- consider that ISIS was shipping ~$160 million in crude oil via smuggling routes to China. Even with all our power, it is not trivial to track such things.
What I am saying is that there are interests here that are enormous and impossible to understand.. some not even based upon nation-state and totally a-political.
The fact that you believe you have a definitive assessment regarding the gas attacks reveals your naivete.
Take a look at the history of the Assad regime and how we destabilized the region by funding his opposition. Take a look at the history of Egypt or Libya over the past 40 years. One day Gadaffi was an American hero, the next day we are cheering for his downfall. Sensationalist stories of rape/murder/torture being spread through the media. The truth is probably somewhere in the middle.
Look at the sort of stuff we spread during the Gulf War: https://en.wikipedia.org/wiki/Nayirah_testimony
This is all to say -- neither of us really knows what we are talking about. But you seem to have a very "good vs. evil" approach to the world that is naive at best.