Okay so you believe that we can't know who carried out the attacks, but it is still right to attack Assad for carrying out the attacks?
Either we know Assad did it or he didn't. If he did it there is a reason for considering a military strategy, if he didn't no such reason. It's like saying: I don't know if he is guilty or murder, but it is good he is in jail for life. It does not make sense.
Then Trump did what Obama failed to do - enforce his predecessor's red lines.
Can you explain what that red line is?
"We will warn you and damage an airfield...somewhat!"
59 cruise missiles won't change anything. It never did.
Fighting against Assad and ISIS and hoping moderate rebels will make some kind of democratic state strikes me as unrealistic.
So the "strategy" is attacks which are designed not to remove (or weaken) Assad, or even prevent him from carrying out further chemical weapons attacks.
so re Assad vs Islamists, Assad is the lesser of the two evils there.
Russia approves of this framing of the situation in Syria.
Got it: Bomb Assad, with the goal of not accomplishing anything, for something you don't know if he did, with the goal of not accomplishing anything of lasting importance because we want Assad to be there. Presumably, bombing him a bit will make him a more reasonable partner later.
Now you lay out your position
I think Syria is lost, partly due to Obamas failure to confront Russia, which was born out of a political climate in the US where Russias involvement in the conflict was mis-understood and mis-represented -- what should be done now is to cut the losses, identify lessons and prevent a similar thing from happening elsewhere, most importantly to understand that Russia fought a proxy war with the US in Syria and won.
The most important lesson to be learned is to identify what Russia is likely trying to accomplish. Russia has been selling modern S400 anti-air systems to the Assad regime. Why do you think Assad wish to buy modern anti-air systems when the Islamic state does not have any airplanes and the regime's economy is likely stretched to the breaking point?
The ONLY party hostile to the Assad regime interested in flying aircraft over Syria is the US, and so Russia is selling these systems with the purpose of shooting down US airplanes. I think it is very clear that Russia is hoping to pull the US further into a proxy war over Syria where US aircrafts are potentially shot down.. with Russian military stationed across Syria such a proxy war would likely be unwinnable at this point given Russias airforce turned the tide against the rebels the past year (remember this was the moves you were applauding).
It takes little imagination to go from that view to an answer as to why Assad would risk a gas attack: Why not? What is the US going to do? Limited military intervention if this type, with a warning, will only strengthen the Assad/Putin bond and give Russia a better negotiation position. Remember Putin is ready to throw Assad under the bus any moment if it means lifting sanctions.
You asked me what should be done. I can't answer that exactly since I am not a military strategist and I do not know what is feasible at this point. I can say that the first thing that should be done is to develop a plan which any military intervention should be a component of; dropping 59 cruice missiles is not part of any plan I know.