Dozy:
I may be contradicted by the report when it finally arrives, but it would not surprise me in the least to discover that what the trim system was doing didn't even factor into the troubleshooting mode (by which I mean mental model) they were in.
I agree that they didn't factor the trim system into their troubleshooting.
Because the trim system (following the sidestick input) held the nose up and kept the Angle of Attack in the stall range, the aircraft continued its plunge to the ocean.
Why didn't one of the pilots do something about that?
It seems apparent that they didn't even notice it.
Why didn't they notice it? It wasn't in their scan because they apparently were trained not to touch the pitch trim wheel(s) since pitch trim is always automatic and since it's automatic, why would you care?
I continue to believe that autotrim should disconnect along with the autopilot. That way, there is no doubt who is in control. That is a pilot's perspective.
The next report will confirm whether or not the plane did just what the pilot(s) told it to do. The bigger question is why did they tell it to do that?