It all starts when Courier 6 delivers a package to Ulysses's new home in the Divide, accidentally triggering its underground war heads and nuking the town. Effectively all single-player RPGs have this, as even if tropes like the Chosen One are avoided, the PC is always the driving force of the game (in a good RPG anyway). Ulysses has a working theory that one person can change the future, for better or ill, and there's a level of meta-gaming there.
Simply put, The Lonesome Road DLC does something no other Fallout game has managed to do: force a player to effectively face themselves.
