Here is a solution for everyone:

If you completed the 7th umbral storyline, the last mission required you to pray at various prayer stones throughout the world. In the End of an Era cutscene, Louisoix harnesses the power of the prayer stones to trap Bahamut but it fails. In a last ditch effort, Louisoix harnesses the power of the prayer stones to send various adventurers 5 years into the future. We need to assume that 1.0 players that did not reach the point of the storyline where they prayed at the prayer stones; were never sent 5 years into the future.

We know that everyone who was not sent into the future had their memories wiped. Thus, we need to assume that 5 years go by, and those who never completed the 7th umbral storyline arrive at their respective starting capitals with absolutely no memory of the previous adventures they partook in during 1.0. Tragic? Sure. But it makes sense.