Obama left a mess where Assad has been free to terrorize with atrocities and Russia has opportunity to expand it's hegemony in the area - Trump wants to extricate us from it but will not countenance the chemical warfare - he's leveraging what is available for the international community and even with the UN - note that the UN Security Council heard all the testimonies and then refused to go with Russia's desire to condemn the strikes...
Trump is walking a line that includes both morality and the right thing - some folks can't stand that......