A postmortem at J J Hospital indicated that Maru died due to pneumothorax, a condition where excessive air enters the lung pockets. “Excessive quantity of oxygen entered his body from the cylinder, which is also harmful. He seemed to have died instantly because of that.
...
I think he died from excess pressure, not too much oxygen.
Theres something being lost in translation. He didnt die from too much oxygen IN his lungs. He had a pneumothorax. Apparently the force of being dragged in, or impact from the flying bottle, hit him hard enough for the lung itself to pop. The gasses leak out and are trapped BETWEEN the lung and the pleural sac. The lungs are compressed and collapse under the pressure.