Fallout does an excellent job at shifting morality - what is right and what is wrong shifts alongside situational and character driven context. It explores the privilege in touting right from wrong when you are not constantly focusing on surviving.
Coop, Lucy and Maximus are all experiencing and struggling with a loss of identity. All three of them are experiencing crisis in their respective belief systems that they have been thrust into as a means to survive. We have Lucy, with her increasingly shaky logic and set of principles that is failing her in a world they were not meant for. Then, we have Maximus', whose carefully constructed idea of a Brotherhood, a collective, surmounting to a moronic thirst for violence and disregard of the individual, treating you boys as pawns in an endless war. Finally, we have Coop, who is a war vet holding on to American ideals that are failing him, and has been lost since the moment his wife suggested they drop the bomb.
It is easy to feel like you know what your morals are when you meet someone who is diametrically opposed to you. We see it with Coop and Barb, Maximus and Lucy, Lucy and Coop, Lucy and Hank.... Over and over again, we see characters defined by the ways in which they are unlike the other. This othering that creates division, a seemingly clear distinction of 'us vs them'.
It is not lost on me that Coop is so set on being alone. He believes that he will be unaffected by the world at large, the world that failed him and everyone else. That zero ties means zero complications. Lucy seeks out help in others because help was always offered and given, and it continues to backfire on her, and she is at point where she is beginning to realize as such. When Maximus lets his knight die, and when the world keeps turning, he realizes that the only thing that matters in the wasteland is that you do what you need to do in order to live.
All three of them are trying to abide by a set of values that is no longer serving them, and thus feeling at odds with their identity that was only ever an echo of who they were told to be.
These characters (as well as a swath of supporting characters) have a world that had been constructed around them against their will, a product of choices unbeknownst to them, that is in the process of falling apart. It is nuclear fallout as much as it is a falling out, as in the exploration of individuals lives being torn at the seams. How every person thinks their way is the only way, and how that quickly becomes the only way they ever know, sheltering them from the often overwhelming diversity of what it means to be human. The Vaults, the Brotherhood, even the Ghouls and every rag tag society we stumble across. People will always try to make sense of the world, build community, and seek out companionship. Our main characters are just extensions of the worlds they come from, wandering in a wasteland that has leveled the playing field - the need to survive.
The end of the world happens because of greedy, rich people who do not have to concern themselves with right or wrong and with surviving. Survival is a think piece. A hobby. A business venture. The rich prey on those with things to lose and things to fight for, all the while reaping the benefits.
Fallout started before the bombs ever dropped, and the beauty of the show is it's set on explaining that to us through memories mirroring the present. History repeats itself as they say, and if you can disrupt someones belief system just enough, you can begin to plant the seeds that there is only one option. A nuclear option. The end of the world does not happen over night. It is instead the culmination of many little, interpersonal decisions, like tree roots eventually cracking open a carefully laid sidewalk.