Board Thread:General Discussion/@comment-6153949-20150120210718/@comment-1784834-20150121035027

The only logical answer is civil war. Rose led a rebellion against the xenophobic gem government when they wanted her and her outfit to exterminate all life on Earth to make way for a massive strip-mining operation. Rose, Garnet, Amethyst, and Pearl were the only survivors. The rest were corrupted and became monsters, and had their heads filled with lies to paint Rose as a traitor and Earth-based lifeforms as the true monsters planning to spread tyranny throughout the galaxy. This is why Lapis was so hostile towards GAP. It was because her memories were altered to make the Crystal Gems look like warmongering heretics, when that was clearly not the case, and her true memories are being forcibly repressed.

Come the season finale, the civil war will start anew, as the previously-corrupted gems are cured and have their correct memories restored, leading to Garnet (Rose's first leiutenant) taking charge of the counterattack to defend Earth.