But that was a team formed a few years after the Broncos when the BRL/anti-broncos crowd was in full swing. Now you'd be entering a market with people who are 32 and under who would've always been Broncos fans.
The closest comparison to the Broncos and a second Brisbane team is with the AFL, specifically West Coast and Fremantle or the Crows and Port.
In both cases the composite team that undercut the local state comp had a rival show up who represented the state comp (Fremantle/Port Adelaide). But the rival team showed up a few years after the initial composite team. This new team would be showing up 3 decades later, are there really all these pissed off people in Brisbane who follow League, hate the Broncos and are somehow willing to support this newly created team? The presence of St George and Souths fans across North Queensland despite the Cowboys seems to suggest that people aren't as willing to switch teams, certainly not in heartland areas where people already care about the sport.
I see what you are saying mate but for some reason the Broncs have never had the whole city buy into them. Originally because of the BRL thing then because of SuperLeague. There honestly is a huge appetite here for a second NRL team. Even if they are people's second team behind their original Sydney team they will draw and rate well. If the Lions and Reds can average 20k then the second NRL team will beat that. Here are a list of home games at Suncorp that will (even with these conservative figures) ensure that they average at least 25k right off the bat:
v Broncos 45 - 50k
v Cowboys 30 - 35k
v Storm 30 - 35k
v Titans 25 - 30k
v Warriors 25 - 30k (more if the Warriors are travelling well)
v Dragons 25 - 30k
If they manage to pull 20k average for their remaining 6 games (pretty low bar), then you have a team averaging 25k.
Of course the team needs to be relatively competitive and there are other variables, but it is more likely to do well than not, it is instantly the second, maybe third highest averaging club for crowds which pulls the NRL crowd average up, plus it gives TV a weekly match in Brisbane which is desireable to them which can be used as leverage at the negotiating table.