I don't think this is the reason, you know the one about Rin dying, just seems a bit childish.
I think he started to indulge into the plan after the Uchiha Clan Massacre, he would'nt blame Itachi since he knew what was really going on (Unlike Sasuke...)
Since he was very prideful of his clan.
But Obito is shown having hatred towards Konoha which would explain it very well.
or
He was mind controlled by Madara and Zetsu, slow brainwashing similar to ROOT's technique. It gave him a completely different view of the world.
I think he started to indulge into the plan after the Uchiha Clan Massacre, he would'nt blame Itachi since he knew what was really going on (Unlike Sasuke...)
Since he was very prideful of his clan.
But Obito is shown having hatred towards Konoha which would explain it very well.
or
He was mind controlled by Madara and Zetsu, slow brainwashing similar to ROOT's technique. It gave him a completely different view of the world.