As a side-note, the Flight Crew have minimal visibility of what’s happening behind them, either outside or inside the aircraft. Thay are almost totally dependent on the CC giving them as much detailed information as possible to form a judgment on the appropriate actions.

The video showing one of the CC, presumably on an open circuit to all crew, indicates what must be going on. And closing that open circuit to make a cabin announcement may not be the most desirable course of action. And I fully understand the FD’s issues in broadcasting from there wearing smoke hoods ... I’ve spent enough time in NBC respirators to know how difficult that can be!