The first novel in the Star Wars: The High Republic narrative, titled Light of the Jedi, has a key scene that explains how Palpatine was able to cut the Jedi off from the living Force during the events of the Prequel Trilogy.
The downfall of the Jedi and their slaughter at the hands of the Emperor was one of the most pivotal moments in the history of the galaxy far, far away. After all, the Sith had planned this return for a millennium, working in the shadows to exact their revenge on the Galactic Republic and these warriors of the light side. The struggle eventually came to fruition through Palpatine, who purposefully used the dark side of the Force to blind the Jedi and block their powers. Dave Filoni repeatedly referenced this in his hit animated series The Clone Wars, and even the films briefly touched on the subject in Episode III.
Now, the new publishing initiative set many years before the events of the Skywalker Saga finally explains how Palpatine may have managed this feat. In Light of the Jedi, written by Charles Soule, a fearsome foe named Marchion Ro imprisons a Jedi Master and taunts his diminished abilities. “My family knew all about people like you,” he says. “They told me what you could do, and how to resist it.”
The antagonist then points to their surroundings, a dungeon where many individuals are being tortured. “They’re not getting out either. If they die, I’ll just bring in more. Their job is to fill this deck with pain and anger and fear,” Ro continues. “Makes it hard for you to think, doesn’t it? Hard for you to call on the Force… You don’t imprison Jedi behind bars. You do it with pain.”
As ScreenRant points out:
This, then, is how Palpatine weakened the Jedi. It was not another Force power at all; rather, it was another aspect of the Jedi trap he had created in the Clone Wars. Darth Sidious’ knowledge of the dark side essentially allowed him to outmaneuver the Jedi, and with the darkness ascendant, they found themselves becoming weaker by the day, less able to call upon the Force for wisdom, and more likely to make mistakes. Little wonder Palpatine encouraged an attack upon Coruscant shortly before initiating Order 66, aware the catastrophic loss of confidence triggered by this would have a further debilitating effect upon his enemies. Palpatine really is the most dangerous, cunning villain in all Star Wars.
Canonically speaking, this revelation from Star Wars: The High Republic actually makes sense within the Skywalker timeline. As Yoda said when he explained the pathway to the dark side in Revenge of the Sith, “fear leads to anger, anger leads to hate, hate leads to suffering.” So, maybe that’s what Palpatine used to weaken the Jedi and corrupt the living Force as well. Though how he achieved such wickedness as to undermine the entire Jedi Order, we dare not think about.