A few stupid wakey fans at a game is nothing like what was suggested re football, very different scenario, unless you are suggesting that 1000s of RL fans would flock to a closed stadium.
NRL no, there were maybe a couple of dozen looking over the fence from there own back gardens not quite the same thing.
As for your suggestion that hordes of football fans spreading the virus, those fans are quite probably same folk that are ignoring the advice already so nothing changes. Besides are the vulnerable not self isolating.
Or are you suggesting sport should never restart?
Where is the evidence that all sport would be shut down if football fans were stupid, govt had already acknowledged they recognise the value of RL I certain societies. They can recognise the difference between football, rugby, golf, tennis, f1 fans.
Besides no games have been played, and no fans have flocked to stand outside closed gates, the fans issue at football is a possible scenario discussed, the other scenario is nothing happens like that and it's fine.