You were able to sum up the entire main plot of Fallout 3 in a few words--that's embarrassing.
Alternatively, that's how literally any story that has ever existed should be. You can summarize down just about any plot to its core points. Here's the main questlines for each of the Fallout games.
Fallout 1: Get a replacement water chip for the Vault.
Fallout 2: Stop the Enclave from enslaving your village.
Fallout 3: Finish Dad's work and bring water to the East Wasteland.
Fallout New Vegas: Whoever controls the Hoover Dam controls New Vegas.
Fallout 4: Conquer Boston under your chosen faction banner.
Let's pretend Tactics doesn't exist.