Gone are the days where you would just have to put the disk in or download the game files. As developers these days are churning out day one patches that are bigger than the game itself.
To play Fallout 76, you are going to need to download the day one patch which consists of 51GBs; mind you, this is on top of the 45GBs of the game itself. So you are looking at a whopping 96GBs.
Bethesda is yet to release the patch notes for this behemoth of an update, but it is safe to assume it only addresses the performance issues which were present in the B.E.T.A.