I'm confused.
The Great War was in 2077 right?
Then why is there:
*40s/50s music?
*cars with fins?
*computer terminals that look like it's from the 1980's?
Actually... The Fallout future is manifest as their pop 50's ideal of what the future would be like ~with nuclear cars, and robots and such, then blown to wastes by a nuclear war to end all wars. It also exhibits alternate physical laws that are in step with their popular fears and ignorance of certain things ~like the effects of radiation actually turning folks into green monsters.
If you look at the series as a whole, you find that it appears that the 50's were gone with the bomb, and those that remain (survived / and their descendants), are just living in the remnants of that old 50's paradise.
You only find greasers and other anachronistic NPCs in Fallout 3 and New Vegas. In Fallout 1 & 2, the only 50's you see is 50's style junked cars and salvage left over from the days before the war.
Still... Fallout's populace has (and will probably always have) the 50's aesthetic for design and parts of the culture.