so we know that madara has rinnegan this is how it happened he used izanga in the battle with the 1 so he didnt die but his left ey became blind then after nagoto died he replaced his blind eye with rinnegan we no this is possible because danzo killed uchia and took there eyes so why not take the same concept to the rinnegan and in reality youd be retarted not to take the rinnegan especially when ur blind