By the reaction of madara when hashirama comments about his brother it makes me wonder that hasirama had something to do with izunas death and that madara really loved his brother.
Thus to avenge his broters death he took his eyes to obtain his eternal mangekyo sharingan and then went on to fight
hashirama
THIS IS MY PREDICTION WHAT DO YOU THINK
Thus to avenge his broters death he took his eyes to obtain his eternal mangekyo sharingan and then went on to fight
hashirama
THIS IS MY PREDICTION WHAT DO YOU THINK