Although they had remained hidden for over a thousand years, the Sith manipulated galactic events leading up to their ultimate revelation in order to slowly weaken the Jedi Order. While seemingly unrelated events claimed the lives of Jedi after Jedi, history would show that the Sith were responsible for instigating these galactic conflicts from behind the scenes.
Darth Bane's secret order had forgone displays of outright power and mastered the ability to pull the political strings in order wreak chaos and havoc and secretly maneuver into higher and higher levels of power. As the Jedi Order fought to maintain peace throughout the galaxy, they fell right into the Sith's hands luring them into the trap of a no win situation. When the trap was finally sprung it was too late for the Jedi to recover and they were all but destroyed. These events chronicle the Sith's secret schemes to slowly erode the Jedi Order's strength.