Time will tell .........
Until the investigation reveals the real reasons for not evacuating the aircraft we are all guessing what was in the Captain's mind but he would most likely be concerned about a fuel fire spreading UNDER the aircraft - as has happened - and then bye bye to any extended chutes on the port side (full of deplaning passengers!)
And was he influenced by his knowledge of the five star fire fighting utilities at Changi? Tossing passengers out of a burning aircraft at night whilst not being totally sure of the external conditions presents a situation where you're damned if you do and damned if you don't!
Keep the pax on board and the aircraft explodes with huge loss of life or put them out and they possibly get incinerated in a spreading fuel fire?
Think I'd still opt for the first choice ......... sitting here with my Chardonnay in hand!