if you actually pay attention to the manga he gave the kages a choice. instead of giving up the 2 lives he asked for, they chose war. that blood is on the kages who couldn't even keep their word to Naruto. and since you you really think this is all about Rin then you must be that stupid. do yourself a favor and re-read the story before coming on here and looking like another hating idiot who knows nothing.
You should re read the manga. You clearly don't know what you're talking about.
He clearly states out of his own mouth when asked by Kakashi "why are you doing this" he replies, "Because you let Rin die." And yet your are trying to say Rin is not the reason?
Obito is like a child, he thinks like a child, and he never matured. He talks about world peace, but yet he starts a world war, that's one of the biggest contradictions I've ever seen.
He became a villain when he saw Kakashi kill Rin, otherwise, he would have left Madara. So yea, the reason was Rin, as he clearly states himself in the manga.
I can come up with a bunch of other things but hopefully your stupidity will be able to understand what I just said.