Lol. NRL Facebook does not attract other/extra new fans. The neutrals have no idea of what is going on! The AFL have the added advantage of universal acceptance in all schooling (Public and private -elite included ) This gives that code relevance to all demographics moreso than rugby league which is confined to mostly a lower socioeconomic demographic. Granted there are people whom are attracted to the game from different demographics but not as much as compared to Aust rules. Another factor peculiar to Sydney is that it is not an easy city to travel around. I note most of the stadiums on Melbourne have a train line servicing them. This is not so for most Sydney football venues.
"Most of the stadiums on Melbourne" f**k me that's some awful attempts at English. I feel for your students.
For reference, there are only two stadiums used for top-grade AFL in Melbourne, one on the western edge of the CBD, the other a very short downhill walk to the south-east of the CBD. Both are serviced by major transport interchange stations and trams close enough to the door.
By contrast, the two major stadia in Sydney are some 12-15km apart, the one near the CBD is an uphill walk away from major transport (hopefully the new tram will fix that if it ever opens?). The other is a 15-20 minute train ride across town. It's not easy to get to. That hampers attendance culture.
As for the rest of your demographics rubbish - it's rubbish. You're talking out of your arse.