Next time you go to one of those NRL games in Vegas, I encourage you to speak to some other people — anyone really. You'll come across people who have been in the LV region for multiple weeks, as I did when I was on a February flight to SFO last year and surrounded by people heading to the game 2.5+ weeks ahead of the match.
If you knew anything about how seasonal routes operate, you'd know they don't operate them for just the time period in which there is the most demand for the particular attraction on the other end.
You can't seem to stick to a single (incorrect) theory about what's driving this business decision.
First, you said it was NYE, CES, general tourism. That's wrong.
Second, you said it was Vegas handing out large sums of cash to Qantas. That's wrong.
Third, you said it was a speculative play to build up bilateral tourism between Sydney and Las Vegas....
Anymore you'd like to throw out?