In Attack of the Clones, after they learn from Obi-Wan about the secret clone army created under the Kaminoans, Mace Windu tells Yoda that it might be time for them to admit to everyone that their ability to use the Force has “diminished.” Why? What were the contributing factors for this to happen?
I believe that the novelization goes into a bit more detail. From what I remember, it was because Palpatine (Sidious) was using a forgotten technique of the dark side to limit the force abilities of other force users. Yoda knew it was happening (The dark side clouds everything), but even he didn’t know who it (they) was/were. That’s how Sidious was able to be in the same room with the Jedi and still keep is true identity hidden.