With Sasuke asking all of these questions, in addition to getting all of these answers, will that consequently make him the new "one that knows everything?" He is now privy to information about Konoha that not even its standing Hokage and advisors know about. Many people debate over a possible "power-up" for Sasuke, but knowledge in and of itself is a dangerous weapon, especially in the shinobi world.
While many people may disagree, I think that these flashbacks are necessary, and there is no better time to give them. Kishimoto's style is very consistent. After Naruto gained his beast mode/the chakra of most of the other tailed beasts, Kishimoto switched to Sasuke, Itachi, and Kabuto. Within that fight we were shown Kabuto's flashback, with occasional glimpses of the Madara/5 kage fight. Kishimoto is using the same tactic now. My only concern is that when we were finally shown Naruto and company again, he was bleeding from the mouth fighting the gedo mazo.. Hopefully we don't come back to that fight to many casualties.
Hashirama and Madara did not start their respective clans, but their ambitions drove them to the seat of power within each. Considering that it took Madara and Izuna's acquisition of their mangekyou for them to lead the clan.. it would seem that Madara was already heading down the wrong path since before his brother died. But why?! I think that it will be revealed within the coming flashbacks.