The Insane Real Reason That Emperor Palpatine Created The Empire, And The Death Star
So why did Palpatine actually create the Empire and the Death Star? We could be easily forgiven for thinking the Empire was created with the sole purpose of eradicating the Jedi and the Republic, and the Death Star to simply keep his galaxy in check after the fact. Well, what if there was more practical reason for this? That is exactly what I'm going to look at here. So let's dive in and look at the theorized reason behind this: something along the lines of an extragalactic invasion like the Yuuzhan Vong War in Legends, which happened a couple of decades after our heroes freed the galaxy and made a pretty firework display out of the second Death Star.
First, we need to look at the fact that Palpatine would never really have needed the Empire to pull off ending the Republic. He did that through planning and intelligence. He maneuvered himself into a position of power within the Galactic Senate by starting a war between the Republic and the Separatists. He used this war to make himself supreme chancellor, which essentially gave him control over both sides of that coin. A position that he used to turn the full galaxy almost completely against the Jedi who had been keeping the peace and defending them for generations at that point.
Now, this did take a lot of planning for the soon-to-be Emperor to pull. However, that is not to say he was not aided by external forces. When Palpatine began to put his wheels in motion, the Republic was already in a mess. The Senate was so bogged down in discussion that nothing ever got done. This was even shown in the prequel trilogy with the endless discussion and no action taken well until Palpatine got himself those emergency powers.
Add to that the fact that, by this point, the Jedi were not really doing their jobs effectively either. How things were supposed to work with the Jedi was they were supposed to act as beacons of compassion and essentially be moderators in any disputes for both sides of a war or even trade agreements that got out of hand. Basically, anywhere you went in the galaxy, the Jedi were supposed to be listened to and respected. This in turn would allow discussion and open dialogue to happen between both parties with a usually peaceful resolution.
However, by the time The Phantom Menace kicks off, this isn't really the case. Yes, I know the opening has Obi-Wan and Qui-Gon attempting to do just that. But in reality, the Jedi Council had begun looking inwardly by that point and were spending just as much time as the senate meditating and discussing the state of the galaxy rather than attempting to fix it. And even when they did jump to help, this always resulted in aggressive negotiations, as a young Anakin would call it.
Basically, this left the galaxy open with little defense in the way to stop Palpatine going through with is plans with no real need for massive fleets or an Empire. And given his intelligence, why did he bother to go to these extremes? He did it because he knew the power vacuum he would create would leave the galaxy open to invasion.
You could even argue that he went to these lengths to keep the galaxy in check and curb any thoughts of Rebellion after the fact. But the Emperor himself never really felt that this was all too much of a threat. That was something that bothered Grand Moff Tarkin. In fact, the Emperor himself never actually sanctioned the only actual full use of the superweapon to destroy Alderaan, which is explained by the rule by fear mantra the Tarkin Doctrine, as the galaxy's media would refer to it as. He was the one who thought the weapon would intimidate the Rebel Alliance and the remainder of the Republic, but this was never Palpatine's intention for the weapon. The Tarkin doctrine did influence how the Empire kept its stranglehold on the galaxy, but it may not have been the only intended purpose of the weapon.
In all honesty, building a weapon with the capability of reducing planets to nothing more than an asteroid field really isn't necessary or practical for fighting a Rebellion who, although well funded, were scattered across the galaxy. And what is the point of destroying planets if the force you are fighting doesn't even control any? There isn't any really. But what weapons and fleets of this magnitude would be particularly adept at fighting would be a force who could transform planets into giant shipyards for the production of Koros-Strohna ships, which were the massive organic ships used by Yuuzhan Vong.
When you look at it, the Republic were never really prepared for an invasion on that scale, and far less one that wasn't the result of someone controlling both sides and never letting either side gain and advantage until the right moment presented itself. When you look at it, the New Republic didn't really win the Yuuzhan Vong War; they lost so much sentient life, a large portion of the galaxy was completely gone, and Coruscant was captured and then terrafomed beyond any recognition. The Empire, despite its undeniable inherent flaws, would surely have been able ensure a far less costly victory over the Vong with a significantly lower death toll given its fleet and Superweapon.
In the novel Outbound Flight, Palpatine said that the Outbound Flight project's path will take people directly into the projected home of an immensely powerful and hostile alien empire, and that he has been preparing the core world for an invasion which he believed would come too soon if Outbound Flight discovered this alien race. You can read about it here in the plot summary on Wookieepedia. So there it is, proof that Palpatine knew that an invasion was coming and even potentially knew it would be the Vong, and all this occurs around five years before the Clone wars even begun. I think it is safe to say his Empire and superweapons were in preparation for something on this scale rather than to take the galaxy or even fight off Luke and the Rebel Alliance.
Source(s): Reddit, Wookieepedia