One thing that has puzzled me, in the interaction between the two copilots. If the Junior one was flying and the senior one thought he was screwing up in a big way, I can see an advisory call of the problem followed by "I have the aircraft" if the senior guy still was not happy with the other man's performance. (And proper CRM says the reverse can happen too). But this apparently did not happen. Was the senior copilot not concerned with the junior one's performance? Or was he too busy with other things?
Is there something exclusively in the interaction between copilots that would act to inhibit this type of takeover of control. Perhaps Captains orders who was to fly a segment?