When it comes to video games especially, there's a difference between being believable and realistic.
My go-to favourite example of this is Call of Duty: Infinite Warfare. Is it realistic? Hell no, there's jets and things in it. But are the events that occur believable? Yeah, I guess.
That's exactly it. In a setting where there's already a massive fleet of Navy Spaceship Supercarriers, it's believeable that there would be the small F-Series inspired spacecraft called Jackals. It's pretty believable that the Navy would have a large presence in space. It's pretty believable that the SDF would be a thing as well.
The main idea here is that "Realistic" in my eyes is relative to real life, while "Believable" is relative to the setting.
An entire organization devoted to fighting vampires? Not believable in Stalker, but definitely in Skyrim.
This is just a more optimistic way to look at games' stories. Do they make more sense in their own context instead of ours?