Unfortunately, there was a lot more going on last night (I assume as the post was made this morning-Friday) that you are discussing events on Thursday night/Friday early am.
I don't know what effect it might have had on this situation, but from about 8pm to midnight Syd/Mel time, brown things hit the whirly things in Sydney and an ATC shutdown/restriction put the kybosh on most flights to and from. So as of this morning both QF and DJ (as well as the others) had numerous crews & aircraft sitting on tarmacs when they were meant to be elsewhere. I would guess getting things back on track on the east coast meant there was nothing extra to be sent west.
Of course the pax are understandably frustrated; there were many in Melbourne who were told a flight was going ahead with exemption from the curfew, only to be told right before departure that the flight was canned. But I did not see any unruly behaviour, only people lining up at the desk to get their hotel vouchers.
What it is about delays in Perth that turn people into chimps? I know it's not everyone but even in the last few months, I've seen some appalling behaviour towards the airport staff. Sometimes the ground staff have nothing to tell. I've seen them heckled for making announcements along the lines of 'we have no new information, boarding is still expected at xx o'clock" Cue swearing & name calling from pax.
It makes me ashamed to be from Perth sometimes! Teresa is right, people never used to act like this. While airlines hold some responsibility for the way they manage delays, pax need to realise they are responsible for their own reactions, and it is NOT an excuse to act like animals.