Winner takes all in the house of representatives. The senate uses proportional representation

The big two parties labor and the coalition change the rules and gimp small parties every time they start to get popular (see the recent party name bans, increase in members needed to register, caps to self funding and expenses)

The actions of the republicans in the US have pushed voters away from the coalition and their leader Peter Dutton (who lost his seat) as they were cozying up with the Trump administration and mimicking them in various ways

Therefore Labor wins