There had to be a catastrophic failure of some sort. Somehow, the report stated that the plane did a sharp straight dive from 28,000 ft.
If there was a seal break, causing a loss of oxygen the pilot could have passed out, if not on auto pilot, the plane would go pretty much straight down.
I doubt there was a lack of fuel, because there would be warnings and the pilot would have contacted someone of an emergency. Another option is fuel that
was either accidenlty or purposely contaminated. There was no indication of a fire in the write-ups but that doesn't mean there wasn't one.
Regardless, it was a tragedy and my prayers go out to all the victems and the families of all involved.