I don't believe (Syrian claims) that many of those tomahawks failed to hit the targets, the satellite images showed 40 or more very accurate direct hits, some would have been multiple missiles on each target. They've improved guidance systems these days, to the point that not only can they reliably hit a building, but choose which window to fly in. It's 2017 - not 1991 or 2003.
Anyway, on the surface of things, the Syrian forces probably used chemical weapons, so they got a hint of what's coming to them if they use them again. If you're going to target anything, then the airbase and munitions bunkers from where the planes alleged to have dropped the chemical weapons departed from seems sensible.
Deeper though, IMO there's a problem. Russia doesn't like chemical weapons and neither does Syria's main local ally - Iran. How much influence they have over Assad - who knows? Russia has geopolitical motives in the ME / Europe. Trump was/is in deep trouble domestically. At the cost a a few dozen cruise missiles and buildings, perhaps a few old cold-war era Syrian planes - if they didn't move them out of the way in time after being told missiles were on the way - this might have been a perfect win-win situation.
It could have been a glorious sideshow, from Bannon being sidelined (but he's still Trump's chief strategist), a precision targeted cruise missile attack on an air-base which destroyed a lot of buildings - but left the base otherwise unscathed - so that it was in use the following day.