Things happen that we have no control over – or, at least, cannot determine. Things happen that are unexpected – that catch us unawares. It's one reason why "The best laid schemes o' mice an' men gang aft a-gley." If your projects are something less than well planned, then you are in even bigger trouble. And if you were flying by the seat of your pants in the first place, then the risks and costs mount. That is what has been occurring to American foreign policy in the Middle East. The phenomenon pre-dates the arrival of the inchoate Trump administration. Barack Obama's amateurish foreign policy team had its own feckless tendencies. Its Bush predecessor at least knew what they wanted to do but lacked a feasible scheme to reach its dubious goals.
There are features of how the United States makes and executes foreign policy that help to explain why Washington is repeatedly thrown into confusion by unforeseen developments. Most significant is a certain linearity of thinking and action. It takes literally the proposition that since the shortest distance between two points is a straight line, the most efficient approach to getting from where we are now to where we want to go is to set our bearings accordingly.