I thought we were talking about descent rate, not Vne.
Agreed on heavy cargo shifting as a potential cause of the problem.
Yeah a normal descent rate would be ~1500-2000 ft.min. From what I've seen/heard so far the plane was in one piece when it went in, but was in a nose dive according to an eye witness. Put the nose down to begin descent and a heavy portion of the load slides forward, the C of G could easily move far enough forward to overcome control inputs. And then perhaps the nose slides even further. She's all over but the paperwork.