IOs problem was the fuel leak unfortunately there isn’t an easy way to diagnose this event from the flight deck except by external observer or as in this case the ensuing fire caused by the leaked fuel. HTH
The pax and cabin crew were very much aware immediately.
The problem is that their information did not get through to the cockpit until much later in the proceedings.
"Remain seated" while a fire is raging nearby reminds me of the advice given to Grenfell residents to remain in their units