something must have gone seriously wrong for the nose of the plane to have declined at such an extreme angle.
"You need something to hold the nose down” said Benjamin Berman, a a former NTSB investigator who has experience flying 737s.
Aviation Experts Baffled By Crash Of China Eastern Airlines Flight MU5735
The only thing that could have done that to the plane, besides the pilot, is the elevator jack screw. Those aren't exactly easy to break, either.