McCain seems to be in favor of military intervention in every two-bit conflict across the globe. Odd behavior for an ex-military guy.
But there may be a very rational reason for McCain's bellicosity. Money.
Going back to the mid-nineties, McCain was vocal in calling for intervention in Kosovo. At the same time, it was also revealed that the Albanian-American National Council (or whatever) was a massive contributor to his campaign fund.
My guess is you'll find a similar movement -- the Syrian-American Friendship Foundation (or some such)-- financing him today.
Senator McCain is neither conservative nor liberal. He is an opportunist -- acutely sensitive to which side is buttering his bread.
Note that it won't necessarily be the American side...
He was also perfectly willing to set up an entity with George Soros, and in short order his campaign staff was pulling in six figure salaries there.