The Captain knows he has a fire despite not having any fire indications in the cockpit, because the tower has told him so.
Apart from giving a "cabin crew at stations" call ( or the Singapore equivalent) what does the crew do?
Contact is established with the FC at 0651:50 around 2 minutes after being told of a fire. No attempt to contact the cabin and establish what they could see. No attempt to turn on the video. No reported attempt to ask the tower.
Instead wait for the FC who inspite of saying the fire is a big one recomends disembarkation not evacuation. The FC was confident he would get the fire under control, however fire is unpredictable. Just look at what happened to that poor firefighter who lost his life in Dubai.
The Captain who is initially evacuation minded, defers to the FC and effectively absolves himself of responsibility and allows the FC to become the decision maker. Perhaps he woild like to donate his salary to the FC as well.