Why did Granny Chiyo killed Sasori?

He lets him live because itachi wanted sasukes eyes because the mangekyou sharingan will make anyone blind. so he had to get sasukes eyes so he wont be blind. But itachi dies trying:) Actually that isn't the case, Itachi never actually wanted to take Sasukes eyes he was only testing his strength/vessel and pushing him to his limit making him run out of chakra and eventually try and force out more power which he didnt have. Because of him trying to push out power that he didn't have sasuke is taken over by Orochimaru, since the repressing chakra which was being used to prevent him from doing so was used up. And because of Itachi's last jutsu, susanoo which is able to seal away souls which is used on Orochimaru. By doing so preventing him from ever being taken over by Orochimaru and no longer relying on the cursed seal. After this Itachi wanders over to him while blocking Sasukes final attacks touches his forehead, and says while smiling "Sorry Sasuke... This is the last time." This is all explained by Tobi also know as Uchiha Madara in a couple of episodes after. Truth is that Itachi loved Sasuke and never could or wanted to kill him, since he was his little brother and only aimed to make him stronger.