Why and how... Did itachi from naruto die?
yeah he die beacuse itachi let sasuke kill him Both of them were weaken and had no more Chakra, Sasuke manage to form a small chidori with no power as he jump down to strike his brother lightning struck down and hit sauskes chidori and powered it up really good but itachi manage to block but itachi was sick for many years he took pills to keep him alive just so sasuke could kill me(he die out of illniss not sasuke), by doing that itachi's master plan went into motion - if sasuke could kill the famous itachi Konoha would welkom him back with open arms and by killing the person most precious to him he unlocked Mangekyou Sharingan, and before dying he tip sasuke forehead to infuse him with Amaretsu and unlocking his final stage of Sharingan the Eternal Sharingan
no, in manga chapter 477, when sasuke is fighting Danzo, Itachi shows up from the dead.
Yes... and sasuke called real lightning from the sky to zap him like a maniac.
yes because itachi cant kill his brother but sasuke can kill his brother.