Henra: "Doesn't fit this scenario.
At all.
Uncommanded rudder trim would cause a nose down dive and a sharp turn."
Well said, Henra. Kudos. The available evidence says this aircraft traded speed for altitude, until it stalled. Why? That's the question. The rudder can't make it climb like that. Stop the rudder nonsense. I'm just a humble private pilot, but this is obvious.