@dozy
the PNF elects to defer the decision to begin corrective action until the Captain
No.
The PNF made his best effort to persuade the PF to put the nose down.
However:-
From memory, meaning I have not re-read the reports recently, I think that there was one crucial moment that set the scene for the crash.
As the Captain left the flight deck he kind of casually inferred that the less experienced pilot (who happened to be in the LH Seat) was "acting Captain".
As it happened the LHS pilot declined to accept the (very good) advice coming from a less (perhaps inadequately) assertive but far more experienced pilot who's role was Pilot Monitoring. Quite simply I suspect that his (the pilot flying's) head was too big for his boots.
I think that this was the Captains crucial error. (Well apart from leaving the flight deck at all given the proximity of the Inter Tropical Convergence Zone and the associated radar visible thunderstorms, which were a mere 10 minutes ahead).
I feel quite strongly that if the Captain had not given the "acting captain" nod to the inexperienced PF that the crash would very likely not have occurred.