Based on one of the greatest video game series of all time, Fallout is the story of haves and have-nots in a world in which there’s almost nothing left to ha...
I don't want to give away too much if you haven't been playing Fallout since the very beginning but the NCR is not started until years after the first game when a person the vault dweller helps, organizes their village to become the New California Republic.
We don't know when this vault opens. It hasn't been mentioned in previous games so it might have opened and failed before anything else from series starts or it will take place many years later and we just haven't seen the NCR and the other factions in the teasers.
True so some time after the Arroyo incident, the brotherhood would have taken vertibird tech from the enclave after the chosen one took them down for the first time.
This assumes the writers for the show give two shits about the lore. They might only use the lore as set dressing for generic post apocalyptic trash.