Rather than why the aircraft went down, I believe the real interest at present must be WHERE IS IT.
Given the total futility demonstrated by electronic means to locate any wreckage, it must follow that the search methods will have to be based on the hydrodynamics of the Andeman Sea and the Malacca Straight.
Those interested in the subject may refer to the American Journal of Environmental Science, 2012,8 (5), 479-488, General Circulation in the Malacca Straight and the Andaman Sea.
Here is a link to it.
https://www.google.co.uk/url?q=http:...W1Bsn20njh-ifA