I don't see that he had much of a choice.
I agree with what he did, however, he had the choice to go to Congress and get permission (which is legal) or to just go ahead on his own (which is not legal).
he saw Obama as flunking his test the first time and looking weak
Even though Trump was against takiong action against Syria at that time, AND Congress denied Obama the approval he legally needed to laynch a strike.
You would think that after 50-60 Tomahawk missiles the Syriain airport would have been out of commission for more than a few hours. How much did those missiles cost?