I don't think anybody said 35kg cats are common, this animal if it was that weight was clearly exceptional. As for being fake, there is a 900mm long cats tail that has to be explained. However the point remains that feral cats substantially larger than domestic animals are common.If you had 35 kg feral cats in Australia, your farmers would be the first to find out. Lynx will take out grown female red deer, adult sheep is just a snack. Your imaginary 35 kg feral cat would have enough power to kill cattle and horses. Cats have different way to kill and eat its prey than dogs/dingo, it can be recognized.
As it happens unusual and unexplained livestock killings are one of the factors used by "big cat" proponents to support their cause.
It is an observed scientific fact that predators, when not suppressed by larger predators, can evolve to take advantage of the prey available. For instance Sri Lankan leopards are the largest leopard sub-species. Without competition from tigers they have evolved to become bigger to take advantage of prey animals such as sambar deer. The Australian bush is full of prey animals ranging from six species of deer to wild boar to native animals such as kangaroos.