A decent number of the 5 million greater Sydney residents are 1st or 2nd generation immigrants, with some pretty big numbers coming each year.
If I moved to a new country I’d probably follow the local sport.
I wonder how many fans the game picks up from the new arrivals? Or how many fans are 1st generation fans (they didn’t pick up the game from mum and dad etc)?
Probably no way of knowing.
if they have kids that are say, 12 to 18 and still at school, the peer group mostly follows NRL and go to the footy with their mates, then they start to follow the footy and their local team as it is part of their new culture. These people would be first generation "converts" and when they mature they produce second generation NRL fans/players
as you say there is no way of knowing the percentages of the converts, but peer group pressure can have a big influence as they want to "fit in"
then there are those who follow football (soccer) as that's what their parents follow, or it was part of the culture of the country from which they emigrated