Why did Australia implement ADS-B before everyone else? Because we could. We have a lousy regulator and a rotten air traffic control system management, so nobody asked "what is the cost of this system and how will it affect the entire industry?".
There were no doubt some technical specialists with time on their hands who thought ADS-B would be "nice to do" and add a fillip to their careers - being able to go to International conferences and condescendingly say "my experience of ADS-b is....", "Our Australian system does....". Then there are all those technical papers to write and publish in support of a doctorate.
I have seen this behaviour before, also at great expense to the community, when Melbourne water outfitted its offices with optical fibre circa 1970. The IT folks admitted that they did it for their careers and out of curiosity. Damn the expense. The technology was then so new that they had to get American defence department clearance to buy the fibre and equipment...
So now the Australian aviation industry is saddled with expense and most probably a substandard implementation of ADS-B that will never fulfil its promise to anyone but a few, and will probably have to be reworked again at great expense as the technology matures. I thought of fitting it, but it makes no sense.