Volume 43 revealed his true intentions. He did what he did to a) Prevent further destruction among nations, b) Save the only one he could save: his bro, c) Save the village, and d) Make sure the Uchiha still have a future by protecting their rep as he became the bad guy.
It all worked and then he joined Akatsuki to just keep an eye on them by himself and keep up with what they were up to (Hiruzen was content with this as Itachi could not pass on intel back- no one else could know the truth so anytime he'd go to Konoha he'd be met with violence). Itachi also let him make sure they did not get Naruto during his lifetime (as he was assigned to capture him but never bothered to seriously capture him at any time) and the organization also let him have a place to stay and get income (as after the massacre- other villages are out of the question, he would never go with Oro, no other place would be willing to take someone from the Bingo book just like that, etc).