The "big picture" is, that forecasting is looking into a crystal ball and trying to find a path which is the "most likely one" without any hard facts underlying it.
Question is: have certain market factors such as unexpected and late promotional activities by key retailers been communicated and recognized we;; before the onslaught? In a certain sense, we could compare that to certain military campaigns (e.g. the Somme, Korea, Barbarossa), where certain elements of information were available beforehand, but were not considered properly.
Peak is peak, and if the operational envelope is not provided an adequate reserve, then the envelope will burst, and damage to the public image will happen; and this is what will be very expensive for a brand.
UPS (as well as others) has as such a finite capacity at a given moment, and if customers (providers of goods) exceed this capacity by willfully changing parameters, then they have to bear the consequences. Communication is of the key essence, especially in critical situations, and there something went wrong which even the best and most adequate planning could not have factored in. In our centres, we had no more space to park cars for deliveries, no more trained personnel (including seasonal) to load without significant levels of misloads. UPS has cut resources to more than eliminating the fat, they have cut into the bones of the supporting infrastructure.
Even though info from the centres where I work is more than ambiguous, the hard work of our service providers could not satisfy every customer. On the preload side, we did what we were supposed to do, but overall, an unhappy customer does have a memory (and the operational personnel on the ground level is not always given the "real" truth"). In the end, he/she/it will come back to us, but with a bitter taste. Major retailers will run their theoretical exercises of " Can we do it better than UPS on our own?", and one day the answer might be "YES".
Numbers are not everything. Eons ago, I worked for an American company, breathing and living by numbers. Today, they do not exist any more as a major factor in their sector of industry. Numbers are not everything. Using information sensibly has become a key factor for planners, and upper management should sometimes listen to those "peons" on the ground ("vox populi, vox dei").