Before the global financial crisis, Australia had a diverse and highly competitive financial system. The four major banks went head-to-head with the likes of St George, Bankwest, Bendigo Bank, Aussie, Adelaide Bank, RAMS, Wizard and Challenger.
Today every single one of these entities has disappeared as a genuinely independent concern, wholly or partly acquired by the majors (with competition concerns waived by the ACCC), or merged with one another.
Before the crisis, Australia's banks were not explicitly government-backed. And taxpayers had never guaranteed bank deposits before (or conceived of providing such guarantees for free as they currently do), nor had they ever guaranteed the banks' institutional debts.