My mind's wide open on the actual cause but I added the dialogue into the equation when assessing their state of brain function. Stress may indeed have played a part in the continued repeating of the requests, but I'm suspicious that the crew did not tell the admirably calm ATC that they were not able to physically navigate towards the Atlantic, except by repeating the question. ATC in fact told them they were continuing to turn left, and the response to that was not normal, even taking into account language and stress. Of course, at that point they may well have been really fighting the aircraft, and may even have had the echoes of the Jakarta flight rattling around in their minds. But they want a big area to splash in, that they're determined about, but where a sheltered river would have given a much greater chance of survival at and after the ditching. However, changing horses on my bet again, they may well have been dutifully trying to keep the population safe thinking they were going to be throwing their charge at the water with very crude control and their minds going from two disparate but horrible scenarios.
So, deeply stressed or affected brains? All bets off now.