That is because Mad Max is a dumbass selfish asshole.
I would be fine with the whole "ammoral anti-hero" schtick if Max didn't flip-flop on it constantly and it didn't lead him to take immensely idiotic actions. I mean, seriously, think of the stupidity of the original Fallout 3 ending multiplied by 5x, this is kind of contrived bullshit I'm talking about here. The whole plot of this game is so mindnumbly dumb that I find it hard to explain, but let me try anyway:
Right at the start of the game, Max's motivation is established; he wants to acquire a really big and bad car with a V8 engine in order to cross "The Silent Plains" with (a place that doesn't really exist and that Max just made up on his head because he is "mad"). For this purpose he basically bullies some mutant dude who also happens to be a very good car mechanic into becoming his servant, the mutant dude is generally fine with that since he sees Max as a holy figure of legend. From then on the Mutant dude presents Max with a car that he is working on, "The Magnum Opus", and promises that he will help Max into building that car into the meanest and baddest road monster there ever was, including the V8 engine he was so fixated upon.
[60 hours of really repetitive open world gameplay follow suit until you have managed to gather all the resources and unlocks for your mutant companion to fully upgrade The Magnum Opus into it's final form]
Nearing the end of the game there is a woman who is trying to seduce Max to try and get him to become her husband, but he shows complete disregard and indifference for her outside of reluctantly saving her daughter because he sort of owed it back because the woman also saved his life once. The last time he sees her, he is repeatedly rejecting her proposals and basically kicking her daughter out of his car and abandoning both of them without looking back.
Then the antagonist who survived a throttling chainsaw to the medulla oblongata kills the woman and the child as a way of getting revenge on Max. Once Max finds out about it, his indifference is all of sudden gone and he becomes totally pissed and angry, to the point where he goes fully insane and starts hearing voices telling him to kill everyone and write the name of the girl upon the sands using their blood, he gets so nuts over it that he almost deliberately kills himself by driving the Magnum Opus off a cliff with the mutant mechanic buddy in the back and everything.
His goal, which you as a player were pursuing for dozens of hours of gameplay at this point, instantly changes from crossing 'nowhere land' in a big bad car to mad revenge instantly, all because of a woman that he had barely any connection to and that he clearly didn't care much about minutes before.
And then, incredibly enough, it gets so much worse... At the final confrontation against the antagonist, Max decides, for no good reason whatsoever, that the best way to destroy the antagonist's truck is to ram the Magnum Opus against it in a way that will cause both the Magnum Opus to be destroyed as well as your faithful mutant buddy to be killed.
Mind you that the Magnum Opus is the one thing that you have been working towards improving and upgrading throughout the whole game and that at this point, after many hours invested into the open world, you already have over half dozen different ways to kill enemy vehicles easily. But no, the game doesn't give you any of the many options of destroying enemy vehicles you had at your disposal during normal Gameplay, the only option to proceed is to comply with the retarded semi-interactive cutscene where Max proceeds to go full moron, needlessly both destroying the vehicle that was the centerpiece of the previous many hours of gameplay and story as well as killing the single most unique, interesting and likeable character in the game; the loyal mutant mechanic who was constantly helping Max throughout his journey in a multitude of ways.
And then the designers decided to make it somehow even worse just to add an extra big spit in your eye; destroying the Magnum Opus and murdering the mechanic achieved nothing at all, the final boss just comes out of the truck instead and "the real" final boss fight begins... and it's the easiest and most cringey boss fight in the whole game...
And man do I wish the retardation stopped there, but I could just go on and on about how demented and poorly written the story in this game is...
I wholly and completely repent having played this game at all. The storyline was so utterly defeating, disappointing and just outright frustrating that it retroactively made the hours of enjoyment had prior feel hollow.
