https://www.chron.com/technology/bus...f-13644104.php
I do know that the cargo airlines don't have to follow the same flight and duty time limitations (FAR 117) that passenger airlines do. There's been a lot of controversy about that in the 5 years since passenger airline pilots started following the new rules but cargo pilots were exempt from them.
That being said, I would be surprised if fatigue had any real factor in this crash. My personal opinion (borrowed from my pilot husband, lol) is that it was a structural failure and the elevator, slat, or something like that came off the plane and caused them to nose-dive unrecoverably. That is one of the few things I ever worry about with my husband's flying. For the most part, flying large aircraft is super safe these days, but sometimes mechanical issues just become too big to overcome.