Almost by definition, Science Fiction is about building worlds. The tales we sci-fi authors spin transport our readers to different times, places and dimensions where things may not be familiar. Different laws and social norms may exist, different species, physics. Every detail may be vastly different.
Our protagonists inhabit these worlds (in general) with ease. This is their normal. Their place they call home and in which they go about their daily business as easily as we do ours.
So why do some sci-fi authors insist on building their worlds on page 1, paragraph 1?
As soon as the novel opens, there’s a story of historical cataclysms and wars a century past. There was a war (of course) or a plague (second option) that tore society apart and caused the collapse of the Neo-Roman Empire and the rise of the Galactic Federation. Or something along those lines as this seems to be a recurring theme.
Yet this grandstanding rarely does anything to move the plot forward. It reads more as if the author wants to show how much thought they put into their world building than any attempt to advance the plot. It has no relevance to the story.
People don’t think of the Napoleonic Wars as they walk down the street.
No, honestly. I am an avid history geek and I can only think of one, maybe two occasions when, as I’ve walked into a shopping mall being trailed by the local secret police, I’ve mused on how the Battle of Waterloo caused a seismic shift in world politics that led to me taking this action at this moment.
Unless your world building has something to do with the plot please leave it out.
If your grand scheme is relevant to the plot by all means let it leak out. Just do it in a way that seems natural. Let details come out in conversation as the story evolves. Small details can hint at great battles far more effectively than spending a paragraph explaining how [made up name #1] defeated [made up name #2] with a cunning tactical move that now bears his name and shall never be mentioned again.
Of course, this doesn’t mean to say you shouldn’t think about these things. Sketch out the timelines and key events and players. Create a wiki and maybe even write the story of the Third Assembly of The Uprising because it might be interesting later. Just don’t feel compelled to shoe-horn it into the your first few pages in the mistaken belief it “sets the scene”.
Remember your characters already inhabit the world you’ve created. They don’t need it to be explained to them and they’ll rarely think about how it got to be that way unless prompted. Let the story flow and the world will wrap comfortably around it.