It is surely elementary that the collapse of the financial system in 2008 caused a huge downturn in private debt and that public debt was forced to get into the act to help prop up demand.
If one combines the sum of private and public debt, Australia will look high relative to other countries (as Australia is a debtor country). See Barnaby Joyce’s piece in the Australian.
But the combination of public and private debt remains below (relative to GDP) what it was in the Howard years. Without public debt, we would be in oddles of trouble.