The president does not make decisions. The presidency does not make decisions either, at least not in the sense that an individual, or a well run corporation makes decisions.
Rather, it is driven entropic forces, which tend over time tend to have certain outcomes, like a river slowly changing its course. Thus we see the presidency gradually yielding on Aleppo.
If Xenophon, or Raffles, or Clive of India, or Atilla the Hun was running the show, he would decide whether to hold them, fold them, walk away or run. What we see the American government doing is drifting and wobbling, and right now it is gradually drifting amorphously and slowly towards abandoning its long held plans for regime change in Syria. By and large, the decisions of the presidency have no clear motive, no clear objective, and are not well modeled as decisions by a self interested individual. When IBM does X, it is generally because the CEO has decided that X would be profitable. When the presidency does something, it is the net outcome of a bunch of individuals each pursuing his particular self interest, each maximizing his particular microslice of power and his particular reputation for holiness, the net outcome of a great many individuals each with a tiny microslice of power each doing something that serves his particular interest, as a river changes its course as the net outcome of the drift of many tiny grains of sand. There are no elders of Zion, or if there are, they don’t care what happens to Zion.
If Clive was running the Aleppo operation, he would fight, or run, or cut a deal with Russia. But the presidency is incapable of cutting a deal with Russia over Aleppo because, as the Russians have discovered, it is “not agreement capable”, a term generally used for failed states. The American negotiators may agree with Russia that America will do X in return for Russia doing Y, but then X does not happen, not so much because anyone in America made a conscious decision to double cross the Russians, but because there is in fact no real chain of command connecting the negotiators with people who might have the ability to make X happen. So the presidency neither fights, nor runs, nor cuts a deal. Today it is drifting slowly in the general direction of running.
The amorphous, erratic, unpredictable, and uncontrollable drift of the presidency on matters of war and peace contrasts dramatically with Harvard’s ability to decisively and abruptly make decisions on matters of faith and morals, for example global warming or second hand smoke. One day every academic everywhere in the entire western world believes X. The next day, every academic everywhere in the entire western world believes Y, and not only believes Y, but has always believed Y, and has absolutely no recollection than anyone anywhere ever believed X, except perhaps a few ignorant bible thumping racist loons in the wilds of Appalachia or the marshes of Florida.