Jammedstab, I think a distinction needs to be made here between fatigue and circadian rhythms. When I mentioned the "C word", I intentionally did not accuse the crew of being fatigued or even tired. They may have been, but we have no info on that.
What we do know is that it was nearly midnight local time, and the flight was originating from a place where it was then 3 AM. Contrary to your suggestion, we can guess a few things about our crew. For example, they were not based in San Francisco. Also, it was probably between 3:30 AM and midnight on their base time.
And here's the thing about Circadian lows: they're not based on fatigue, but rather what time of day your body thinks it is. Industrial accidents have their highest rates between 2-4 AM and 1-3 PM, and that's with people who are well rested, sober, and in the time zone.
Sure, most crews pull it off just fine. Most times, you'll get by without the last five minutes of final reserve fuel too.