What bugs me with the hypoxia hypothesis, is that the first actions are to put your masks on and establish comms, and only then do you start the descent...
I agree, which is why I suggested 'creeping hypoxia' due to failure to pressurise successfully. I do however find it difficult to understand how at least one of the pilots wouldn't have managed to get some oxygen, even in a partially hypoxic state but as I posted earlier, hypoxia affects perception before it affects consciousness and to put the mask on you need to be aware that you need the mask in the first place.