I've always thought that this story was (a)unlikely, (b) jumped to the easiest answer by blaming the pilots, and (c) thus gave a good excuse for the airline and the Malaysian government.
The dailybeast.com has a long series of articles that demolish this suicide/terror theory and point to a much more likely explanation: a fire in a two-pallet load of lithium batteries irresponsibly stored in the forward cargo hold. The fire would have knocked out the electronics in exactly the ways that they failed. Unable to communicate and deprived of the flight control system, the crew used the autopilot to turn towards the nearest usable airports in Malaysia and Vietnam. But they were probably overcome by poisonous gases generated from the over-heated electrolyte. The gases killed the passengers and crew before they were aware, while the airframe withstood the fire and flew on until it ran out of fuel.
Memoirs of a Turkish F-4E pilot during Operation Desert Storm
50 years ago Air Force Magazine - A Mach 3 transport?