If Mad Max were like Batman, he'd be a 'road warrior' with a background appropriate for his time and place, rather than being an anachronistic ageless policeman. That is absurd as if someone made a batman movie with '40s batman but set in 2016. Being a 'road warrior' embittered by failure but still trying to help people is an ageless concept. Being an australian policeman is not.
i suppose it's all subjective interpretation, because when i watched 'fury road' i simply saw it as "there's this dude, he used to be a cop, he's the connective tissue that links stories set in a post-apocalypse environment" - the character of max and his details are largely irrelevant, because while he's technically the protagonist of each film his character itself isn't the focus.
the only reference in fury road is the opening monologue "i used to be a cop. a road warrior, searching for a righteous cause" - which if you want to get really fanboy arguing about it (which i don't care enough to do, but will do to play devil's advocate and for the sake of wasting a few minutes at work to type this out) doesn't give a definite timeline or say that he was a cop or a road warrior BEFORE the collapse of society... or, that society is universally as degraded as this one area the film focuses on.
hypothetical example: there's a scene in fury road where they're discussing trying to cross the salt flats, or going back to Citadel. max says "you can ride for 300 days and i promise you'll find nothing but salt" - i know nothing in the movie specifically indicates this, but i've always found it an interesting point to wonder if he's right.
okay so it's a semi truck retrofitted with battle gear. based on the RPMs and MPH gauges shown and guesstimating based on the visual distance between Citadel, Gas Town, and the Bullet Farm (which seems to be like 10-15 miles at most from each other), the entire drive that takes place in fury road starting at Citadel and ending at the start of the salt flats couldn't have been more than about 200 miles (for the moment ignoring some serious issues with the movie's chronology vis a vis drive time).
so if we assume that the movie takes place in australia, for all we know the whole thing happens out in the middle of the border between the northern and western territories, in the gibson desert... this whole movie could be happening just a few thousand miles from sydney, brisbane, and melbourne, except nobody knows those cities are still more or less intact, and nobody in the cities knows about a few hundred nutbag desert cosplayers running around in the middle of nowhere.
(side note: i know this is going to absurd lengths just for the sake of a discussion about a movie, but it totally works)
i always kind of imagined that max was in a more populated region, had bad shit happen, then went off his nut and ran out into the desert and it was more or less pure coincidence he bumped into Citadel.
that's perhaps how he knew for sure that there was nothing east across the salt.