Supplemental oxygen is available to pilots as a secondary source of oxygen usually as a pressurized mask in larger aircraft. Gradual loss of cabin pressure can go unnoticed by pilots and cause hypoxia over a period of time. I'm not sure if this is what happened to the pilot but it's a possibility.
Are you for real? They get him down to 11,000 feet in this clip - easy breathing altitude. The crew has recovered, so it's back in their ballpark. Plus, where is the emergency cancelled? It isn't. ATC is still working on getting them to their destination. The captain said he wanted to go to Yip, ATC don't really have a say in that. I'm honestly not sure if you're serious or not because what you're saying is incredibly detached from reality.
Listening to this again, it’s clear that there are missing segments. There is no order from atc to descend to 11k, probably because they did it in a way that did not comply with anyone's procedures; their memory is affected, still groggy. Incapacitated copilot wondering why they are at 11k and running out of fuel? That is reality.
@Blaze0357 Good question. I've been to 13000ft in an unpressurized helicopter and felt some of the smaller effects of hypoxia, but I didn't realize it until after descending a couple thousand feet.
That wasn't the copilot; it was a pilot on another aircraft re-stating the voice communications since ATC was having a hard time understanding. The copilot was already unconscious when this conversation was taking place
i) At flight altitudes above flight level 350 unless one pilot at the controls of the airplane is wearing and using an oxygen mask that is secured and sealed and that either supplies oxygen at all times