The green card process wasn't specifically helped by being Australian but more by being from a country that does not submit a lot of green card applications.
There's a rate limiting approach so that countries can not use more than a certain amount of USCIS's application processing bandwidth. Currently China, Mexico, India, Honduras, The Philippines, El Salvador and Guatemala are being "rate limited".
Here are some tables about the backlog for each country in each category: https://travel.state.gov/content/visas/en/law-and-policy/bul...