Sasuke's goal had been a lie the entire time.
The reason he left his home, his friends, it was wrong. It did not exist.
His mind was reeling. This man had to be lying. Itachi was evil, and he never was more than that. He had no ulterior motives for killing his entire family other than to gain power, right?
That is all he had wanted. There was no way Konoha had actually authorized his acts. It was impossible. They were barely capable of an act of violence against those who needed to be eliminated. Never would they kill their own. They were weak, riddled with emotions; they just could not handle it.
Then why did it make sense?
Itachi had been all he had growing up, the perfect brother. He had loved him with all his heart. He still loved Itachi. Sasuke could not help it, especially after seeing him smile like that as he died.
Itachi was dead. He would never be back.
Sasuke's heart (hey, where have you been?) was suddenly being tied in knots. His lungs had ceased to function.
Sasuke could never let go of what he had been put through. He could not forget his past, and he would not forgive those who wronged him. His grudges were the kind that lasted.
He would find the people who ruined his life (and Itachi's life). He would become an avenger once again.