Thinking about how ultimately Palpatine being the only one truly benefiting from the dark side out of all the movie era sith is completely intentional on his part. His apprentices are all crippled by the way they draw power from their own self-hatred and personal suffering as opposed to the suffering of others. Maul was an abused child lashing out at the world, Dooku was a deeply depressed old man who resented his own inaction and complicity in the perceived corruption of the Jedi Order, particularly his role in Galidraan, and Vader, his magnum opus, draws his power from his own constant agony, and his hatred at himself for killing the Jedi, the woman he loved, and his unborn children. And this makes each of them immensely powerful and incredibly unlikely to turn on him until he discards them, as they all remain so self-absorbed and focused on their suffering that they fail to see the outward systemic cause of it.