I personally think you could very easily divide the main series fallout titles (and 76 because IDK if it's main series or just a spin-off or what) into the west vs east coast games. Not gonna say one is objectively better than the other, but I personally like the story of the west coast games better.
I personally think both sides bring something unique to the table that shouldn't be underestimated, so I don't necessarily give hate to one side or the other.
In lore? The East Coast was struck a lot more compared to the West Coast, there are many more population centers and important strategic assets to bomb compared to the East. Therefore the people were set back much farther and rebuilding civilization takes a lot longer. Also, the lack of a unified government forming and rebuilding caused major delays in rebuilding on the East. The NCR really jumpstarted the West Coast’s recovery. The closest we can see in the East was the Provisional Comminwealth Government but that was swiftly destroyed by the Institute and all that remains are small settlements.
In Real Life? Bethesda is bad at dates and times and wanted to do funny things, it’s the same reason why food is on store shelves for the player to find and every ammo box still has stuff for you.
for your last point, fallout 3 was originally going to be set like 20 years after the bombs dropped, but they switched it to 200 years somewhere down the line in devlopment
the 20 year thing makes much more sense in some areas, like the lady in arefu who is pretending the world didnt end
It's actually kind of my major (and basically only) beef with the show. The West Coast was basically recovered, it had this whole story arc where the NCR was playing out the American cycle again including a Manifest Destiny idea, humanity never learns etc, and then it just collapses because Todd can't be trusted with other people's toys. Like, the NCR had more than one city, and more than one important city, it was like pretending 1812 America would collapse because Washington DC got burned.
Developing World: You stole our water and supported the installation of brutal but market friendly leadership that's friendly to exploiting our resources and people for foreign profit! We're desperate and dying!
Market Capitalist World: glug glug glug sorry, we couldn't hear you over all this thirst quenching!