Other officials involved in the crash investigation have suggested that either of the plane’s pilots might have commandeered the aircraft in order to commit suicide
I'm not aware of any credible evidence that proves the pilots were responsible. The pilots might have been wrestling to control the aircraft for all we know and flying it around the coast to avoid crashing over populated areas. Something else might have caused multiple debris fields thousands of km apart, with the aircraft eventually coming down. For all we know the aircraft might have lost a key control component over the South China sea and dropped some debris there and then limped back to Malaysia and beyond.