User blog comment:Justice Avenger/Which young heros you think should be added to The Team?/@comment-5141417-20120617000119/@comment-432124-20120623002724

OK, so you're asking why the Legion would want to go back in time to fix something that happened a thousand years in their past. Maybe you need to ask yourself why they would do that in any universe, because that what they have done a bunch of times in the comics and a few times on other TV shows.

Maybe on Earth-16, like in the comics, the Legion could have been inspired by the Justice League and possibly the YJ team, and so whatever happened to the JL and YJ could have affected the Legion and their home worlds in a big way. Therefore, if the world in 2056 is devastated so much that Mount Justice is in ruins, the 30th and 31st centuries could have been devastated in the same way, if not worse. Therefore, whatever Legionnaires there are left would have to go back in time to find the source of the dystopia and prevent it from happening in order to fix their future.

As for the exposition, you should know from reading what Greg has said in his interviews that, even without the Legion, there are gonna be a lot of new characters, good and bad, from a lot of other worlds being introduced and playing big roles this season and with that will come a lot of exposition to be covered. So we wouldn't be spared much exposition if the Legion doesn't show up.