what could drive Itachi to genuinely turn on Konoha?

[[ Funny you ask….

Itachi discovering that Danzo sent someone to kill Sasuke, for one. Itachi asked for one thing, and Danzo cannot even hold up his end of the bargain? Slimy old man, Itachi’ll pull out Danzo’s entrails himself. He’ll release all the information he has.

Also any situation in which Sasuke gets killed in The Leaf and Itachi can pull mental hoops to blame it on Hiruzen. Which, it’s really easy for him to sklklflksl. 

His POV is that Sasuke is not supposed to die, at all. I’m sure he doesn’t know about most near-deaths (he likely gets outcomes instead of exactly what happened), but death? Not allowed. He left Sasuke there so he could live, not die. 

Don’t get Sasuke killed. ]]