A couple of thoughts:
- was this captain more worried about cancelling the flight and messing up the schedule etc. at the expense of the well-being of her/his passengers? Is that why she/he kept them onboard for so long?
- did he/she leave the flight deck to see what the situation was in the back?
FWIW, I've had a couple of similar experiences, both well handled.
1) BA @ Naples. There was no air-conditioning in the cabin while we waited for clearance to push back and start engines (I don't remember why). The temperature was becoming unbearable. However, I
do remember that the captain kept the passengers informed regularly and said that if we had to wait much longer, he would disembark us. That reassurance helped. Was any given here?
2)
Ryanair @ Nimes in south of France. Awaiting clearance due to the ATC delays in France last year. We waited on the tarmac for ages. The 'mature' American captain left the front door open and kept coming back into the cabin to see how things were. From my brief conversation with him, he definitely did not strike me as as SOP-before-airmanship man.
Same airline, probably different crew showing how it can be done properly.