Maybe that's just what Vault-Tec wants you and the general public to believe. It's highly suspicious that we don't encounter anyone else from the Vault. Highly convenient that we wake up from a "hangover" and are all alone from then on, even though our peers were supposed to be the best of the best. Nobody bothered to come wake us up? Not even the Overseer?
Perhaps it's all a lie. What if Vault 76 only collected the brains of America's "best and brightest" in twisted experiment to pour the collective skills and knowledge of various humans into a single superhuman, using whatever dark science or simulations were at their disposal? Once the experiments were complete, the super-survivor's memory was tampered with, and the scenario we play through in the beginning plays out like a well-scripted performance.
To summarize, Vault 76's only living occupant was the player character, they were subjected to horrific torture and experimentation by the Handy robots, and then manipulated using drugs, carefully placed notes, and computer terminals into doing Vault-Tec's bidding. An even darker story than the default, but perhaps not as depressing.
