Star Wars: Episode II - Attack of the Clones exposes the Separatists' droid factory on Geonosis, but the Clone Wars show that it was far from the end of their army. Although they lasted for only three years, the sheer scale of the Clone Wars was nearly unprecedented in galactic history. This was in part because the bulk of both opposing forces was made up of, effectively, mass produced soldiers: clone troopers on the side of the Republic and battle droids on the side of the Separatists.
The concept of using droids for combat was perhaps inevitable, and as such battle droids existed in one form or another long before Darth Sidious began his scheming. In the later days of the Galactic Republic, Droidekas and B1-series battle droids notably fought for the Trade Federation during the Invasion of Naboo, shown in Star Wars: Episode I - The Phantom Menace, but their true interstellar prominence (and a corresponding proliferation of varieties) would come more than a decade later, with the outbreak of the Clone Wars.
Contrary to appearances, Geonosis' massive droid factory was not actually destroyed during the engagement shown in Attack of the Clones, but later in an episode of Star Wars: The Clone Wars, after the planet was briefly recaptured and then lost by the Separatists. Although this factory, and others on the desert planet, produced much of the initial stock of the Confederacy's battle droids, including new models like the B2-series super battle droids, it was just one example of many such complexes. Baktoid Combat Automata, the company responsible for the production of the vast majority of Separatist battle droids, was owned by the Techno Union, which, like the other major corporations that supported the Confederacy, was interplanetary and boasted a presence in many systems.
The wealth of possible locations for additional Separatist droid factories is a good reminder that the Clone Wars were farther-reaching than could ever be depicted in the films or even the show. Because the construction of a droid army would have aroused the suspicion of the Galactic Republic, the factories responsible would have been hidden away on distant planets loyal to the Separatist cause from the outset. And given that one of the founding principles behind the formation of the Confederacy of Independent Systems was a disillusionment with the influence of the Core Worlds over the rest of the galaxy, many of their member systems would be so far-flung as to be outside of the effective reach of the Republic even when the war began. The resources and locations available to the Separatists for further factories would have only grown as they recruited more systems to their cause during the Clone Wars.
The potential for confusion over the destruction of this particular facility may be owing to the fact that it differs from the usual focus of the Star Wars movies; unlike the destruction of the first or second Death Star or of Starkiller Base, which were singularly significant, the sacking of the droid factory on Geonosis was only one of many important instances in the three-year-long conflict. And while the Battle of Geonosis was significant in that it began the Clone Wars proper, it was also indicative of many similar kinds of battles that would be fought over the coming years as both sides of the conflict burned through considerable resources all across the galaxy.
