It doesn't mean football is big in Australia, it means Australians like to watch their sports teams do well.
What were the audience figures for Torvill and Dean's gold medal performance in the UK? Apparently, 24 million people watched it. Does that mean ice dance is a big sport here?
This isn't big ... it is biggest ... of all time in Australia - that's astonishing in my opinion.
Australia have won the rugby world cup twice and been in the final on two further occasions (note that when people decide to watch a match they don't actually know who is going to win). Similarly Australia have won the cricket world cup five times, and been beaten finalists twice. On one occasion for each sport Australia was not only finalist, but also host, which tends to add to viewing figures. We are told that Australia's sporting national obsessions are rugby and cricket and that football isn't a big deal.
Yet the Australian team in a semi-final (not even a final) in football drew a viewing audience bigger than any of those finals appearances (where by definition their team had got further than the semis) in their so-called national sports. Or any other event in the history of Australian tv.
I think it is remarkable frankly, and really not what I would have expected.
Oh and on your Torville & Dean comment - was this the most watched tv event of all time in the UK. Is it in the top 10 most watched tv events of all time in the UK. Is it the top tv sporting event of all time in the UK. I think you may well know the answers to those questions.