Why the "if'. The Swans did drop away and they came through. All clubs drop support in lean patches just as clubs gain support in purple patches.
You can't compare that to footy heartland clubs because they're heartland clubs, your fairweather support drops away. The numbers of the 'through thick n thin' fans are still high though.
In contrast it's fair speculation that Syd fans that are 'through thick n thin' is a very much smaller percentage and the exception rather than the rule. That's very hard to argue.
Bris is another good example, the gabba has been an echo chamber with almost zero fans in it for the last decade. 2019 and all of a sudden msm, and fans who think Dan Rich is a qlder come out of the woodwork.
Whichever way you boil it down and dissect it there is heartland and syd is not one of them. A generation away at least - this discussion is way way too early.