Jet Upset
A “ Jet upset “ is a strong possibility.
Any distraction to the flying of the plane or a control problem at altitude can become a crash.
As the aircraft approaches high Mach speed the lift moves back, due to Mach effects. The nose lowers more and only in lower thicker air does the elevator have sufficient control authority.
Most modern airplanes have a Mach Trim, which will apply nose up stabiliser to help control this effect.
The issue is, if the plane’s speed is not controlled adequately early on in the descent, then the airspeed loads or manoeuvring loads in the lower thicker air can destroy the airframe.
See Wiki for “ Jet Upset “ and also “ China Airlines 006 Feb 1985 “.
The 747 tail plane has chunks missing from the near supersonic descent. It’s incredible it survived.
( Apparently part of the reason the 747 survived is that some of the gear fell down, breaking the up locks as it was pulling 5 g, the extra drag helped to limit the airspeed.)
So this aircraft ended up going very fast with bits falling off it.
Loss of control at altitude due to Mach effects can lead to rapid airspeed build up and excessive air loads in lower thicker air.
This 737 unfortunately seems to have had a very rapid descent, for whatever reason leading to inflight breakup.