Madara, without his Rinnegan or even a Sharingan, was blind. He had needed to steal Hashirama's Senjutsu Chakra to activate his Hashirama Chestface's Sage Mode, thereby granting himself all the abilities of Sage Mode. Madara himself was surprised that thing even worked, considering it hadn't even been in his original plans, but then again, if he looked back a lot of things had gone his way, so clearly some sort of outer god thought his was the right path and was helping him.

Regardless, he gained a picture of the battlefield, granted to him by feeling the chakra of all living things around him.

Unfortunately for him, Kunai aren't living things and thus don't possess chakra of their own. Thus, Madara could never see the single kunai that pierced his skull coming. He might have heard it, but he'd never been one to put much emphasis in any sense other than his sight. Common Uchiha problem, from what I hear.