As always with accidents, lots of holes in the cheese but, AFAIR, no-one has yet mentioned:
The circadian rhythm makes people’s desire for sleep strongest between midnight and dawn, and to a lesser extent in mid afternoon. In one study, researchers instructed a group of people to try to stay awake for 24 hours. Not surprisingly, many slipped into naps despite their best efforts not to. When the investigators plotted the times when unplanned naps occurred, they found peaks between 2 a.m. and 4 a.m.
The accident happened at 04.47.