Fallout 76: 6 Important Trailer Clues You Totally Missed
1. Reclamation Day
As Country Roads winds down, we're given a glimpse of Vault 76's atrium, apparently after a party. There is a football pitch, several Vault Boy cutouts, and loads of balloons and streamers. Hanging above it all is a huge poster of Vault Boy cheering for 'Reclamation Day'
This seems to confirm the idea that the inhabitants of the vault launched a campaign to reclaim the Wasteland. They didn't need to clean up after their party - they weren't coming back! As the TV voice then says "In Vault 76, our future begins." This irrefutably proves that the vault was set up to re-conquer the Wasteland - you don't pack that many balloons if you're planning on living peacefully.
The game is set rather early on in the Fallout universe - perhaps this game reveals the beginning of an important faction, such as the Brotherhood of Steel. The lore is fuzzy on when exactly they started operating in the wasteland except that it was prior to 2134 - making the dates work well.
Interestingly, we've heard of Vault 76 several times before, in Fallout 3. In the Mothership Zeta DLC, There are logs of a man who was inspecting the vault when he was abducted by aliens. And in the Citadel's data logs it describes how Vault 76 was a control vault with no experiments, to be opened after 20 years. This clearly went wrong, if it's been 37 years since the Great War - or our protagonist just never left.
The Citadel computer also confirms that the vault is in the DC area. It seems we're heading back to the Capitol Wasteland.