Board Thread:Theories and Speculation/@comment-31099706-20170327120301/@comment-25645405-20170405021342

People seem to miss that Itachis Eye is heavly weakend at this point of the story. Meaning Tsukuyomi is also not at its peak of strenght. Additional to that Sasukes Curse Mark Power, which boosted his Sharingan allowed him to break out of Itachis Genjutsu more easily next to the experience he had with Tsukuyomi on top. Itachi also didnt went all out with the Genjutsu, since Sasuke's brain wouldn't be able to recover from that. Imagine what Torture Sasuke would go through being hours and hours in the Genjutsu, while only seconds have passed in the real world.

I also wouldnt go that far to say Itachi went all out on Sasuke. He just pushed him to get him to the point of Orochimarus break out. Itachi planed to get himself killed by Sasuke, but ultimately died of his illness because Sasuke was to weak.