The problem, according to Zachary Feinstein, is that technological terrors don't come cheap. Or, as a certain Sith Lord might put it, the ability to destroy a planet is insignificant next to the financing it takes to do that. In the case of the Death Stars, if you assume their costs were in line with an aircraft carrier's, that was somewhere in the neighborhood of $193 quintillion for the first one and $419 quintillion for the second. That probably would have been too much for the Empire to afford—21-figures is a lot of money on even a galactic scale—especially when it would have been wary of raising taxes too much and fueling more discontent. (As much as you might want to forget, it was the taxation of trade routes that started pulling the Old Republic apart). The upshot is that the Empire must have built the Death Stars with borrowed money.
Make that a lot of borrowed money. Even if the Empire had rather optimistically paid back half of what it owed on the first Death Star, that would still leave $515.5 quintillion in debt—or around 11 percent of galactic gross domestic product. We can get that last number by assuming that the Death Star cost as much relative to its economy as the Manhattan Project did to ours. So, as you can see, that's no moon. It's the mother-of-all financial crises just waiting to happen. Think about it like this. The second Death Star's destruction not only meant the end of the Empire's dreams of planetary genocide, but also of the Empire itself. There wouldn't have been anyone left to pay the banks back the $515.5 quintillion they were owed or to guarantee their deposits.
The banks, of course, couldn't repel losses of that magnitude. So it would only be a matter of time until their depositors found their lack of capital disturbing, and the resulting bank run brought down the entire galactic financial system. Unless, that is, they got a bailout. The problem here, though, is that the banks wouldn't have just faced losses on their Death Star loans. All this political uncertainty would have sent all risk assets down and made people pull their money out of the banks preemptively. That means it would take a bailout of something like 15 to 20 percent of galactic gross domestic product to prevent a complete collapse. And that's money that the pitiful little band known as the Rebel Alliance wouldn't have had.
The lesson, then, is that it's harder to win the peace than it is to win the war. Getting rid of the Empire wouldn't have been enough to bring back the Republic so long as the galaxy was stuck in "an economic depression of astronomical proportions." The fact is that financial crises almost always increase support for far-right parties, which, in a galaxy far, far away, would most likely mean an inter-species war. It wouldn't take much of that for Imperial nostalgia to start kicking in. And considering that the Empire seems to have come back in the new movie, something like that must have happened.
Don't underestimate the financial power of the Dark Side.