If it works the same as here, the insurance company pays for the car, then takes and sells the salvage piece. A good GC with no motor would pull in a good price at an auction the professionals go to, because somebody is sitting with a drivetrain with nothing to put it in.
I New York State, where I worked as an adjuster, a car was automatically declared a total if the damage exceeded 75% of the book value.
Sometimes, the shop wants the car and exaggerates the estimate to total the car, then bids on it. But that wouldn't happen in Australia.
There are so many variables it's hard to know for sure why it was totaled.