From my point of view I don't think they chocked as I never expected them to win.
They play most of their games on the much smaller SCG ground with 90% of the crowd behind them then they come to the larger MCG where Hawthorne play for most of the year.
I know the AFl are trying to give Sydney a leg up in Sydney but they are not doing them any favours when the GF is played on such a different ground and conditions and the ump did his very best by giving Buddy a free kick every time he went near the ball, but I couldn't believe how Sydney could be favorites, but thats just me.