In hindsight what a ****head!
Yes, there have been lots of unintended consequences of introducing species. But was the science and knowledge available at the time. Australia and NZ are so remote that their ecosystems are unique, and many species have been introduced causing huge problems. You would think the snake and dingo population might keep rabbits in check.
Rabbits are not native to the UK, they were introduced by the Romans but didnt really get established until the Normans reintroduced them. However we have predators to keep the population in check.