Board Thread:Naruto Discussions/@comment-1411686-20180619053129/@comment-734582-20180619114708

Kisame seemed either bored, or fed up with people who weren't as decisive as he was. Obito offered him an interesting job and he took it. Apparently initially working for the Hidden mist but eventually working straight for Akatsuki.

Though his actual motivations were never terribly clear. He seemed to think he was like Itachi, someone who had no other place to stay.