Obito has changed radically as a result of Rin’s death – his attitude and demeanour are completely different now, and Madara saw that immediately when he came back (the only sign of his old self surfaced when he spared Kakashi). And as a totally different person, he’s now far more willing to listen to Madara’s plan of creating his world of dreams, where even dead people can come back to life. I’m still finding it strange that Obito suddenly changed completely – it’s true that you can create whatever you want in the Infinite Tsukuyomi, but surely even if he dreams up a Rin, it’s still a fake Rin. All he can bring back is his ideal of Rin, not Rin herself. I’ll put that aside though – let’s just say he’s not thinking rationally out of delusion or something.
Madara made a lot of plans before he died – even saving Obito was a calculated choice he made, as he’d be able to control the Mazou with Hashirama’s cells (though the opportunity presented itself to him through luck). Although Obito did indeed impersonate Madara and do as he was told, Madara must have had to put a lot of trust in him, especially as Obito may have backed out along the way while he was dead. And he even managed to put his real Rinnegan eyes into Nagato, which confirms an earlier suggestion many moons ago that he wasn’t born with them. Jiraiya’s belief that he was the destined child of prophecy, and the reincarnation of the Rikudou Sennin who would influence the world with his Rinnegan wasn’t quite right in the end… but more importantly, how the hell do you transplant in a pair of eyes without anyone noticing, much less the recipient himself?!
Obito’s first meeting with the Ame Orphans was all they showed of his time in Amegakure in the manga – unfortunately, the majority of this double episode was filler. It’s unclear how they’re going to be proceeding from here on out, but I think they’re planning to use the Akatsuki (who, hilariously used to be a chivalrous group working for peace and cooperation) and their back story to highlight how the despair-filled prophecy Obito gave them came true. I mean, look at how happy and idealistic they were! Their dreams are definitely going to get crushed horribly next week, with Danzo having decided to purge them by tricking Hanzou and instigating a conflict between them. And we all know how that turned out.