If you think about it, Madara has been around since the first war, we know he survived up until the third war, and he was revived back into the 4th war many years later. I dont care if your the most blood thirsty solider out there, after so many years of fighting and suffering your gonna get tired and eventually want peace. We are talking about approximately 80 of war at least, plus the one that is ongoing now. It is overwhelming for any solider to live through for that many years.