There is also another possibility - sloppiness in maintenance. Some years back, Taiwan's state-owned airline - China Airlines - had a plane (a 747) that also broke up in mid-air. The cause was diagnosed as maintenance issues - parts were not replaced when they should have been, leading to stress cracks accumulating until they disintegrated the entire plane in mid-flight.
The pilots didn’t transmit anything after the plane was in trouble. Those were all automated transmissions from the plane’s systems. The last actual communication from the pilots was quite a bit earlier, and quite routine, just noting thunderstorm activity which is to be expected along that route.