Rogue One: A Star Wars Story is finally here, and the vast majority of fans and critics agree that it is a very good Star Wars movie. Somewhat because this movie enhances what we've already seen in other Star Wars movies. Mostly Star Wars: A New Hope. However, Rogue One does help fix a pretty big plot hole that exists in Star Wars: Return of the Jedi, too.
Warning, there are spoilers ahead for Rogue One: A Star Wars Story. Easily the biggest threat in the history of Star Wars is the dreaded Death Star. The first one was destroyed in Star Wars: A New Hope, which was able to be accomplished thanks to the plans obtained by the Rebels featured in Star Wars: Rogue One. It took the Empire quite a long time to complete that first Death Star, as the plans for it are first seen in Star Wars: Attack of the Clones, meaning that it took nearly 20 years to complete. So, that begs the question, why was the Empire able to construct the second Death Star so quickly?
From the time the Rebels blow up the first Death Star to the time we see the nearly completed second Death Star in Star Wars: Episode VI - Return of the Jedi, it has only been about four years time. That means the Empire was able to significantly cut down their build time. For quite some time, this has been something of a flaw in logic that Star Wars fans have sort of had to overlook. Thanks to Rogue One: A Star Wars Story, as well as the Star Wars novel Catalyst, we now have a very good reason for this. The main problem preventing the Death Star from being completed had to do with powering the weapon, not the construction itself. After the completion of the first Death Star, that problem was solved, and the Empire could just get to it. They just had to rebuild everything.
The building of the second Death Star does seems like a major continuity problem, but in all actuality, building it was quite simple due to the Empire's methods of construction. Everything was automated as much as possible, and the actual building of the core structure itself was done at tremendous speeds. The Rogue One tie-in book explains that the Empire strip-mined astroids, and even worlds, to get it done quicker. Chancellor Palpatine knew the Separatists also had these plans, and he used that in persuading key military leaders that the Old Republic had to make the superweapon first, before their enemies did. The speed bump did not come in how fast they could get the Space Station put together.
Rogue One and Catalyst work together to give an inside glimpse at how all of this played out, and how it was no problem to whip up a new exterior to house their deadly weapon in Jedi. There were no problems with construction, just with the immense power source. In Rogue One: A Star Wars Story, we see Galen Erso (Mads Mikkelsen) being recruited against his will to help the Empire figure out the Death Star in terms of its actual use. Because he is a brilliant scientist that understands what is at stake and what needs to be done to make it work. It is his knowledge of Kyber Crystals that ultimately helps the Empire power the Death Star, but being a pioneer in this research, it took years for Galen to overcome many difficulties and roadblocks in getting the station to work properly.
Those who have read Catalyst get a much better sense of this. Also, it took the Empire several years to track down Galen and once they did, he was doing his best to buy time and stall as long as he could. So that helped make for the elongated build time on the first Death Star. When it comes to the second Death Star in Return of the Jedi, it is a copy. All of the guess work had been taken out, and the Empire knew where and how the energy source needed to be stored and surrounded, and protected. It didn't leave huge holes in the Death Star that couldn't be covered up until everything was in place. The rush job on the second Death Star actually accounts for the reactor's core vulnerability, allowing for it to be destroyed a second time. They made it super fast, and it became a literal powder keg.
When it came time to build the second Death Star, there is no doubt that the Empire strip-mined asteroid fields once again for raw materials. Automated construction continued, and was done at high speeds. And the physical labor needed was all done by slaves, who are believed to have been treated quite terribly.
This is all explored in some of the new Star Wars novels and other areas of the expanded universe. Once Galen gave them what they needed, it was much easier to build the second time around. Not only that, but they learned a lot doing it once, so they were able to expedite the process the second time around. So while it wasn't a giant, gaping plot hole, it was definitely something worth questioning. Thanks to Star Wars: Rogue One and Catalyst, these questions have been answered.