I'm gonna go with what might be considered a troll response and ask: who the hell cares?
This is most likely the worst, most ridiculous plot twist I have ever read. Ever. It's as if he's trying to create an excuse for the Uchiha to act like that. Not only that, but even more focus and depth about a dead clan instead of the smaller ones? To me, this just seems retarded, utterly pointless and quite frankly, it doesn't make any sense at all.
So now we have to try and understand all those conceited bastards trying to take over the world, or what? And why would we hear anything about Izuna from Madara now, when we know absolutely nothing about him, nor his relationship to Madara.
It's so IDIOTIC!