Here is a simple question. If I intended to crash an aircraft in deep water why would I turn Westerly when I could turn Easterly and fly to the deepest water on the Earth in about the same flight time?
1) Few or no countries to overfly post the first 1 hour of confusion
2) Little or no radar coverage once you swing west and then south
3) Little or no air traffic on that route except for a couple of EK flights
4) Total opposite direction to where one would look (if not for INMERSAT then search would have still been on in an easterly direction using the Helios thought process or at best in the BoB).
5) Little or no boat/sea traffic in that area
6) Flying in darkness throughout with a dawn water splash down
7) Well out of reach of most if not all countries SAR
8) Deep enough water
But most of all...............250 tons of metal still remain hidden almost 50 days later even with a proximate location......so if it went South then it seems to be hidden well enough with no debris showing up.....