Well, the timeline of when the apocalypse happened is a bit weird -- like did it happen in the lifetime of Max himself or not? And is Max supposed to be exactly the same person in each movie? I'm not even talking about the actor change in Fury Road -- I mean in the first he's living in a grim near-future (but not destroyed) Australia, and the following movies present an ever more sophisticated post-apocalyptic society with their own cultures and traditions that would need time to evolve. It isn't even clear if the characters in the recent two even know about pre-war civilization. One of the trailers for Furiosa claims that it is set 70 years after the apocalypse. So how could she have met young Max in Fury Road? He'd be in his 90s at least.
The framing of most all of the Max Max movies is that they are stories being told by an unknown narrator. So any variation is fair game, I think. Unreliable narrators and such. In the context of the new movies, they've even created characters who have the job of remembering and telling the stories -- which is another really imaginative and compelling elaboration on what was merely framing in the earlier films.
