Without knowing the setup, it’s all guesswork- But if I had to guess, the program the robot ran through would be a series of movements that results in a box that is this size and this shape in this position being moved perfectly well to this particular spot.
Humans are not that size, that shape, or in that position.
I’ve not worked industrial in Asia, but where I have worked there has been stringent protocols around locking out machinery that has the potential to kill. For someone to enter a hazardous area, they have to remove any potential source of energy (eg, disconnecting power to motors, draining hydraulic pressure, lowering suspended loads, etc) and use a lock that only they have access to to prevent that energy returning. I’m guessing that this incident either did not have that procedure in place, or it was in place but not followed correctly.