Humans will begin to make errors and experience difficulty assimilating information at early stages of hypoxia but without losing consciousness. It is impossible, in this theoretical scenario, to predict the effect of hypoxia on the awareness and decision-making abilities of these pilots ...
So they were hypoxic enough not to descend but alert enough to program a new track to Penang, randomly add waypoints beyond Penang, their assumed alternate, oh and then the FO picked up his phone to try to make a call. He must of rallied very well an hour after this "explosion".