Unlike the US, COVID was essentially controlled in Australia until some very specific violations of quarantine happened - and the outbreak traced to these violators. These outbreaks weren't of iffy origin, they were clearcut linked to these perpetrators.
In an era where governments everywhere are going authoritarian it only takes something like this to be used as an excuse. The trouble is there'll be little complaint from the public as everyone is aware of the causal link to the outbreaks - and the Australian public, like bloody-minded sheep, is too easily spooked when governments crack the whip.
Unfortunately, Australia is a very conservative country and the vast majority of its citizens do what they're told without question even when government makes crazy decisions, so we've a double-whammy problem/excuse when a few people go feral.