This campaign is intended to be limited in duration and intensity. It is not intended to oust Assad. It is not intended to eliminate chemical weapons. It is meant as a message, and only a message that there will be limited consequences of low intensity and short duration that falls short of regime change and elimination of the ability to use chemical weapons if a red line is crossed.
The volume of the debate in Washington and how this matter is characterized by the peripatetic press (Look! There's a squirrel!) is absurd. This is not a decision of great import. Bombing will have no lasting impact. I would guess that why opinion polls show overwhelming opposition.