Board Thread:Naruto Discussions/@comment-26567684-20150819061606/@comment-1018594-20150819155632

Shin studied the Uchiha clan while he was with Orochimaru. From there, he learned about Itachi and developed a fixation on him. He chose to revive Akatsuki, because he believed that peace caused stagnation to human evolution. And, based off of what our translators have to say, the word choice of the characters in Chapter 700+10 imply that Shin died of his injuries.

As for the whole Orochimaru body thing, it doesn't really affect the plot much, so it wasn't addressed. Kabuto and Orochimaru were probably pardoned for saving Sasuke from death and reanimating the Hokages, both of which helped the Allied Forces win the war. If Sasuke can ally with Akatsuki, infiltrate Kumo, be declared an international criminal, kill a Hokage Candidate and still be excused, Orochimaru and Kabuto's crimes look way less severe in comparison.