Actually, that's not quite correct. Melbourne's major period of sprawl was done with rail in the first place! Their sprawling subdivisions were all created with no automobiles available, just land speculation and trains. There was no implementation of expanding the rails into the auto driven suburbs, as the rail was there first.

Furthermore, it was off synch with the rail expansion of the rest of the world; there was a craze in much of the world to tear out rail lines in favor of cars. It just happened that when this craze was in effect, that Melbourne had only recently installed much of its rail, and so it would be absurd to tear it out. When it came time to tear the old rail out, the fashion had shifted, and the rail lies were considered such a high point by the rest of the world that they convinced the auto-centric government to leave the rail in.

Melbourne's transit system is a mess in other ways; there are vast numbers of transit vehicles off doing their own thing running empty because they will not coordinate, and would rather extort subsidies from the government for running empty on dysfunctional schedules. Travelling across the city by transit was a joke; my favorite incident was in riding a train into a station, seeing a bus pass as we pulled in, leaving the station via dirt trail, walking around a cyclone fence to a six lane highway which we were forced to jaywalk across as there was no pedestrian crossing anywhere in sight, then walking several blocks, passing the person who had gotten off the bus and who had wanted to get on the train we had disembarked from, to reach a vandalized bus shelter and wait a half hour for the next bus which was scheduled the same way.

Much of these problems stem from the privatized nature of the transit systems in Melbourne, which costs the residents a substantial amount of taxpayer money which is used to subsidize poorly designed private routes which aggressively avoid working together. They are underutilized in part because they all run with different bus stop signs and appearances which make the system confusing and invisible. They compete to take people from where they all gather to the other central hubs, but none of them want to touch bringing people to and from those central locations to begin with. They leave a maze of different systems on different schedules designed expressly to make it hard to transfer between them. Transit systems need free market forces like a person with a nut allergy needs peanut butter based cleaning supplies and a lifetime supply of walnuts.