This question basically stems from Air Algerie Flight 6289 1, 2 , which crashed mainly due to pilot error combined with engine failure. One thing in particular that intrigued me is that in both Mentour Pilot's Youtube video and the Wikipedia page, it was stated that the captain's last minute decision to take control was a bad decision that contributed to the crash.
He was originally the Pilot Monitoring, or the Pilot Not Flying (PNF), and the first officer was the Pilot Flying. Immediately after the engine failure, he declared that he is going to become the Pilot Flying, told the first officer to let go of the controls, but didn't know what to do himself.
My question is, is this a bad decision simply because the captain wasn't prepared to handle the situation (since he was chatting with the purser and skipped the briefing), or is it a general rule of thumb to not initiate a change of roles in the middle of an emergency (impending stall in this case)? Is it generally applicable that the captain should not take over, or is it the opposite, that the captain actually should take over the controls in an emergency?