Underfire, wondering if the pilots cognitive performance was reduced due to their workload and hours of wakefulness and sleep history and the stage of their circadian rhythms isn't an excuse, it is common sense. The job they were doing at the time of the incident requires a certain rate of cognitive processing, any neuro scientist will tell you that the rate of processing can be affected by the above factors.
We have an incident where the cognitive process clearly failed, to not look at something that is known to affect the process is irresponsible.