You don’t think it would have been weird for the commander of the Death Star in SW not to be present in this movie, which ends right before SW?
The story was about stealing the Death Star plans. It didn’t have to have Tarkin or the Death Star in it.
The only thing that had to be in the plot was the rebels stealing the technical readouts of the battle station. Now, if you are going to write a story about that, how would you envision the rebels doing such a thing? Where would they even find the technical blueprints for the battle station? What kind of security would they have to bypass? How would they even discover where this place is? I think these are the kinds of things one needs to consider when they sit down and write a story.
It would be very plausible that the plans would be located at a research and development facility. Most probably, that would be the research and development facility where they actually did research and developed the design for the Death Star. Then, the rebels would have to find out about this place from their spies. And they would have to infiltrate it or attack the base and steal the plans and get out of dodge. That would be the plot of the story.
None of that requires the actual Death Star being in the movie. It doesn’t require 10 different star systems and a research base where Galen dies and another place where they store the records. It doesn’t require a THX style data gripfinder just because well, that would be cool to put it in the movie because we saw it in some other movie before.
This is all fanservice schmuck. The kind of stuff people put in movies so they can wink at each other and feel smart and better about themselves, and the people watching the movie can think about how they saw the same thing in other movies and feel smart and better about themselves.
And it sucks.