and then MH 370, which is the only 777 that has crashed over the ocean and the transponder was turned off, no pilot in his right mind would turn that off, it was done maliciously.
Well that's the million dollar question.
The current top theory is the lithium batteries on board started a fire, once that happens, all bets are off as to what technical issues happened with the plane.
Yes, there was a cockpit fire near the pilot's oxygen system in a different 777 (on the ground). It seems plausible that a cockpit fire could have disabled much of the electronics, could have motivated the pilots to turn toward the nearest airfield, and could have incapacitated the pilots. When the fire penetrated the hull, it would have caused decompression that could have starved the fire for oxygen, leaving the people incapacitated and letting the plane continue on autopilot until it ran out of fuel.
It also seems plausible that the pilot could have deliberately disabled systems, depressurized the plane, pointed the plane out toward the middle of the ocean, and committed suicide, taking the passengers with him. He may have killed himself by depressurization, leaving the plane to continue on its course until running out of fuel.
Either way, after the fuel ran out, the plane would have glided down to the ocean surface, in cruise configuration. So far, it seems like the flaperon piece is consistent with that, though I'll wait for the authorities to fully investigate.
Both main scenarios have legitimate criticisms, and I haven't seen a convincing argument to rule out either idea completely. People try to invoke Occam's razor, but in this case, the "simplest" explanation depends on whether you find it easier to accept the human or the machine failing in a particular way. Whether it was man or machine that failed, it wasn't a common everyday failure.
If the wreckage of the main portion of the fuselage and/or the black boxes are found, it will almost certainly rule out one or the other of those scenarios. There will be a burned hole in the cockpit or there won't.