I'm not sure why they've had so much trouble "trying to" get rid of Hilali or the Mufti position. It has been in the press though in Australia that in fact many have, at least, tried to get rid of him.
My guess is that there are two main variables as Fred Nerks has mentioned: a)Hilali represents the "Lebanese Muslim" community (largest muslim community in Australia and especially Sydney)- they seem to have a substantial political clout. b)The Australian government (especially State government which is labor/leftist) hasn't addressed the issue of Hilali.
I think those who want to get rid of Hilali and the Mufti position need to have 'active & visible' support from mainstream and especially the Australian governments (Local, State & Federal levels).
This issue needs to be addressed at multiple levels. I also think that Hilali has been a smart political player thus far. That is why I believe, like many Australians, that it is a terrific thing we now have his stance out there and wide in the open. I think it should be addressed quickly and effectively and set an example for the rest of Muslim fundamentalists in this country.
BTW - when you say a large number of Muslims in Australia, you have to put that into perspective too. There are approx. 400,000 Muslims in Australia (taking the high end) and the total population of Australia is approx. 21 million. Out of approx. 400,000 muslims, Hilali only represent a very minor percentage. Now, I don't want to focus on numbers, but the point is that we need to address any radical muslim elements in Australia efficiently and effectively.
As I said before, we can't allow this to carry on for another two decades or even a few years - I believe the muslim community can't do it on their own but will need to take the lead on this issue.
Probably there's a great deal of money flowing in from around the world to support him.