That's my gut feeling Nitpicker.
They turned SW (smoke), DP, all incapacitated and kept going and going.
But have no answer why all went quiet on the comms front. If the electrics all died that transmit that stuff, surely the AP went out as well?
Malaysia and Indo would be understandably quiet on how an unexpected aircraft at FL 200 could transit undetected.
That's my least implausible theory anyway!