New Evidence in China Crash Suggests Midair Breakup

Authorities have found potential aircraft debris 10 km from the main wreckage site, raising questions about whether it caused or resulted from the nosedive. The nosedive was unusual, occurring at nearly the speed of sound, and debris was found on nearby farmland. Investigators are examining the cockpit voice recorder, which is damaged, and are searching for the flight data recorder to understand the aircraft's performance before and during the dive. The aircraft, a 737-800MG, is designed not to dive aggressively, suggesting possible aircraft failure or pilot action.

What is the significance of the cockpit voice recorder in the investigation?

What kind of aircraft failure or action is suggested to have caused the aggressive nosedive?