Great photo! It’s a 30mph curve and the engineer tried to take it at 80mph. It doesn’t take a rocket scientist to figure out why the train continued on a straight ahead trajectory and came off the tracks.
I have no way of knowing for certain, but would guess that the speed was a lot lower than 80 mph, otherwise the front engine and cars would have flown a lot further down the bank and interstate. What is more likely is that the train was slowing from that earlier speed to around 40-50 mph but it was still going too fast to take the turn. Apparently a passive computerized system that is designed to be a fail-safe against human error was not yet operational (local news report said scheduled for next year). The curve is preceded by a long (if slight) downgrade and so possibly the engineers misjudged the rate at which they could slow down. Time will tell, but I don’t think there’s any chance that rear engine would have stopped where it did going more than 40 mph.