Both cats and tigers are cats, but their bodies are completely different, which is determined by genes. Without changing genes, their body shape will not change, and biological evolution is more in the direction of adapting to the environment. After all, natural selection, survival of the fittest is a natural law, but the current natural environment is obviously not enough to support the emergence of larger animals, because some large carnivores have been difficult to survive. Tigers and lions, for example, are not so easy to hunt. All kinds of creatures are evolving in the direction of small size because they consume less energy.
Australia is a very special continent because it is really isolated from the world. Except for the transportation industry, almost all other places have no connection with this place. Therefore, the Australian continent has also preserved many ancient biological species, and their biological evolution seems to be different from other continents, because the three continents of Asia, Europe and Africa are theoretically connected, and land can reach another continent by crossing a certain terrain, but Australia is different.
Nowadays, cats have gradually become one of the main pets kept in people's homes, because they have no particularly high environmental needs and are not much different from humans. In fact, it is ok for them to eat whatever they eat, because all the domestic cats raised at home were human, and then they could live a healthy life. As for cats that can't eat salt, this habit seems to have come from the west, because most of the cats raised now are pet cats, so they are very harmonious.