It seems Djokovic went through all the proper channels to get an exemption and visa. Australia's institutions gave him a visa.
The real exemption is that a minister is disregarding Australia's institutions and cancelling his visa because "feelings".
Australia needs to take a hard look at their laws and the way they treat their citizens instead of creating a high profile scapegoat.
But most likely this is all an intentionally concocted distraction from government's failings in the current outbreak.
Why did it take a last-minute act from a minister to revoke his visa?
The reason none of this resulted in his visa being refused in the first place is that the Australian tennis folks are buddy-buddy with the Prime Minister’s folks, and the unofficial ministerial guidelines are that if there’s an event associated with government cronies then all stops are pulled.
No doubt very true for the first round. On the second when things go belly-up, as here, they'll scatter like wildebeest being chased by a lion. The second time usually brings unwelcome exposure and much else.