Maybe, just maybe, as Trump entered the position of being president of the USA he was informed about things he was not aware of as he was just an "ordinary citizen" and not the leader of the most powerful nation of the world. Your actions tend to change as your information base changes. Maybe Russia and Usa are fighting for control of Syria, and that's it. Which I see as most likely situation for now. Nothing to do with democrazy or bullshit like that. Trump didn't realize how important it would be for Usa to gain control of Syria, somewhat. And now he does. Simple.