Here are (some of) my thoughts on the matter.
Early in 2013 a tragedy of monumental proportions occurred. Peter Parker (the once and future ) died. Well, technically, since he is only a fictional character, he was actually simply (once again) written out of his own series (the first time it happened, was back in 1994 – 1996 during the so-called Clone Saga). In issue #700 of (Cover dated March 2013) Peter Parker “died” and his long-time Nemesis, Doctor Otto Octavius (colloquially known as the supervillain Doc. Ock) somehow managed to swap his and Peter’s brain patterns so that the then dying Ock was not the hale and healthy Parker while the hero Peter’s brain patterns wound up in the diseased and dying body of Doc Ock. (Don’t ask how all of this was even possible, this is, after all, a comicbook.) Suffice it to say, that with issue #700 of , Peter was “Dead” and Ock was now “Superior” Spider-Man