One theory of mine is that Sydneysiders are (were?) generally more flakey than Melbournians. I lived in Sydney for a year in 1998/1999 and my fellow employees had ZERO attachment to the company we worked at. I can imagine what the Greek Sydneysider's were like.
I doubt this is a thing. Whatever Sydney Greeks jumped on Sydney fc would be insignificant compared to the amount of Greeks that jumped on MV, and here they even brag about changing teams!