Itachi saved Sasuke with Izanami. Sasuke would not be alive without the Izanami technique which Sasuke did not know but hopefully learned from Itachi. Kabuto came back to save Sasuke because Izanami made him accept himself and his fate from his actions. He woke up when he did so and directly came to save Sasuke. Itachi chose not to kill Kabuto and instead use the Izanami technique for the very purpose of later saving his brother and inturn saving the world. Itachi saved the narutoverse. Itachi may have been that smart.