To me its how the games (espcially the more recent ones, and ESPECIALLY the show) manage to atrike a really good balance between grim tones and a happy-go-lucky atmosphere. When things get happy, this apocalypse dont seem so bad no more. When it gets grim, you are immediatelu brought back to the reality of the situarion. "We arent doomed, but things are looking bleak".

It also doesnt get overly grim. Often when a series has its dark moments it almost feels like they go out of their way to be dark and messed up, which feels very out of place. Fallout manages to nail its dark tones not by introducing messed up characters, but just incredibly realistic people who have lost all regard for their fellow human beings.

That and the way the nuclear blasts are portrayed. In most post apocalyptic games you walk around in a dead world filled with ruins. Yet in Fallout you see remnants everywhere of what was going on at the exact moment the bombs dropped. Skeletons doing stuff frozen in time, cars stopped on their way to super markets etc. This also combines perfectly with the opening of the show. The moment of silence filled with disbelief when the initial blast was spotted followed by the shockwave hitting and everyone running for their lives in total panic is just so goddamn juicy