Unfortunately PILOT SUICIDE is the most likely reason for this crash.
Rudder hardover, Stab trim runaway, mishandling a depressurisation WILL NOT result in a descent profile like this. I’ve tried it in the sim and the descent profiles are NOT near vertical like this.
SILKAIR flight MI 185 is a very similar example to compare. Deliberate, sustained pilot input with stab trim at full manual nose down and a high thrust setting was determined as the cause of this crash by the NTSB as an addendum to the final report.