India was looking outward for territory to expand in, since she was badly overpopulated and short on resources.
There's a good reason why Australia has only 14 million people - most of it is desert. Even though Australia is a modern, progressive, technically advanced nation, it's not economically feasible to support a whole lot more population than it already has.
You could relocate a population the size of New Delhi or Bombay, either of which is about the population of Australia. To move more people there, you're going to need an iceberg convoy out of Antarctica (with its attendant problems of weather and military vulnerability) or a commercially-feasible desalination system.
If you've ever been to the Los Angeles area and driven east, you can see a very similar situation. LA was originally a seaside oasis on the edge of a desert. The city covers where the oasis used to be, and not far to the east it's still desert. Despite ridiculous property values and Romanesque aqueducts, it's still not economically feasible to continue urban development to the east.
India is big enough to build or buy enough hardware to swat Australia like a bug, but just because Australia is "land" doesn't mean they can populate it like India.