Board Thread:Theories and Speculation/@comment-28323245-20170530200422/@comment-734582-20170530213604

It seems that the Mangekyou needs not just the death of a loved one but also the death of a dream.

Itachi's dream of a peaceful resolution was lost when Shisui died. Obito got his when his dreams of seeing Rin again died. Sasuke got his when his dreams of restoring the Uchiha's honor died, since he kind of cut down the one guy trying to save it.