Democracy Now sprang up in the Lyran Alliance in the Jihad, but was crushed pretty quick by state and noble forces.
Yes, just like many Republics in the middle ages. I think people's attitude was generally that Republics work on a small scale, and they are good in theory but bad in practice. It could even be argued that Republicanism goes against human nature, since it is natural to want to give titles and lands to one's heirs instead of society as a whole.
However, at a certain point, because of certain conditions, Republicanism did break out first in the Americas, and then in the very heart of feudal Europe which was inspired by the events of the colonies. This then made Napoleon, who was chosen to lead the military because he had a win rate of 80-90% vs. other generals with 30-40% when France was losing on all fronts. In fact, the situation became so dire in less then a year, Royalist forces outnumbered Parisian Patriots-Republican soldiers 2-1. The defense of Paris on that day was conducted by Napoleon, who saved the Republic, and made it last 15+ years after in the face of Seven International Coalitions, which could at times include a dozen kingdoms. War at this time underwent a Revolution as well, as Napoleon introduced several innovations. One was marching separately but fighting together. The second was the Corps system, in which no army was more then one day's march from reinforcements. The third, was living off the land and in bivouacs, which allowed him to take many more soldiers then otherwise (this was already to an extent in place, but Napoleon would bring it to an extreme. ). He created a National Bank, which not only funded the military, but reduced inflation from over 100% each year, to something like 0.7%! He instituted a total war policy - even old men and children could be used for the war effort by passing out pamphlets, women could make clothes for the men, workers munitions, etc. This could allow him to almost match four to twelve nations against one (in trial terms, that means he could fight 6 or 12 to 1 "trials" usually to a decisive victory and then near standstill) . And he likewise utilized an army based on merit instead of birth right. He was also employing Citizens and Patriots, fighting for their own nation and liberty as opposed to mercenary and those coerced by their Feudal Lords. To this day, military historians call it "the dawn of modern warfare. "
My point is that the political revolution was accompanied by military revolutions which made it last a lot longer then "Democracy Now!", it was accompanied likewise by the Reign of Terror, which did effectively cow the aristocracy in France. Ironically, the Reign of Terror was paired with the idea of a "Republic of Virtue", until the author Robespierre was himself beheaded.
So it was a combination of factors, all favoring each other and giving opportunity to one another at once. Ultimately, to defeat Napoleon, even his enemies had to become more like him. They had to re-organize their armies into modern armies instead of utilizing the feudal formula. This removed the 'raison d'etre' (justification for existence) of feudalism on a martial level. Armies from then on would be Nation-State, not Lord-Vassal. This, along with multiple other changes, helped ensure the survival of the Republic for a decade and a half almost across all of Europe.
That was a product of 17th & 18th century nationalism more than a product of revolutionary thought. European monarchs such as Louis XIV had already successfully subordinated local nobles into palace courtiers & replace feudal levies with regimental commissions. Feudalism aa a military institution had been dead practically since the reconquista.
Claueswitz himself notes, at the dawn of the Napoleonic Wars, most armies were largely composed of a Noble leading mercenary forces of on average 20 to 30 thousand. These generally clashed in border, territorial disputes with not much wagered and not much gained.
By the end of the War of the Seventh Coalition, armies had grown to six-hundred to eight-hundred thousand under singular commander, and 900,000 (France) to 1,200,000 (Britain), including Reserves, overall. The very scale of warfare had changed forever in a relatively short time. This was also aimed at Capitals, nor borders, which were seen as by and large irrelevant to the specific war at hand. I believe Clausewitz compared it to people dueling with wooden swords, only to have someone with a real sword sword come in and start chopping off arms.
The English & Dutch merchant classes had already been international powers for two centuries by that point! ;D
And both had to scale up their trade to contend with Napoleon's continental system, and both nations ended up facing financial strain because of it. In fact, many of the times England sued for peace at all was because it was near financial ruin by over-extending for war efforts. However, the real issue is how constraints on the "middle classes", merchants and industrialists were lifted. Their trade powers increased over ten-fold, and they became far more International, in part because Britain advocated international trade as a weapon against Napoleon's continental system. The Republic, by contrast, simply got rid of a lot of feudal constraints, though it is fair to note the Continental system that very much damaged his empire held constraints of its own regarding trade with England. Piracy likewise grew at this time, as did smuggling. The point was, the Middle Class and Traders gained a tremendous amount of power and rights, and that could not simply be undone, especially with so much of the nobility increasingly going into debt.
Not to create too much of a digession from your original post, but Stone to me is a poor man's Bonaparte, & the Bonapartes were no democrats. Does Battletech need democracy? No, democracy is terrible for war, dull in creating narratives, & wouldn't leave anyone in office long enough for them to become interesting in the fiction. Let my knights in shining 18 meter tall armor remain knights, & battle one another for glory & honor.
I'm not talking about democracy though, simply Republicanism. All that means, is rule with no feudal lords or monarchs. An actual Nation-State instead of a kingdom. A Republic can actually change its form of government to suit its needs, just like France did, employing both democratic and autocratic elements, while multiple critical parts of the feudal order, namely the least efficient and credible ones, are systematically reduced and then eliminated. Even after re-taking France, the Third Estate (Commoners, which includes emerging Financiers and Industrialists) had become so much more powerful and used to their rights, and war had changed to such a degree that bringing back the old order was impossible on all levels but the generally superficial. The Emperor of Prussia, for example, became little more then a figurehead by the time of Moltke the Elder, and the advent of the General Staff.