In the Orientate phase of the OODA loop one of the elements to be considered is the genetic make up of both yourself and your opponent. One aspect of that make up is the mental energy level of yourself, your team, and your opponent during the process.
Research detailed in Kahneman's book "Fast and Slow thinking" indicates that there is a clear linkage between mental energy and decision making. If someone or a group has been struggling with a difficult decision and then is asked to consider a less difficult but still challenging problem they will not think creatively about the matter. They are more likely to go with their default attitude, revert to the norm as it were. Their mental energy or ego has been depleted.
You know that it exists, just cast your mind back to a decision you made just after a stressful discussion. Did you bring a fresh vigor to the decision or did you either go with the prevailing opinion or accept the solution that was being proposed?
This situation typically occurs during meetings with multiple items on the agenda. If a group has struggled with a difficult problem or one with sharply divided opinions then having solved that they have a reduced appetite for more contention. If you have two or three contentious items in a row the mental energy depletion is manifest and subsequent items will be given very short shift.