he also invisioned Rin being killed before he arrived on the scene
obito said he thought it was raining, but it was his visioning of rin dying or kakashi crying
since obito supposedly slipped into madara's cave, i suppose one of the zetsu were around at that time watching
Obito's fight and waiting to get the sharingan for Madara to have another eye maybe, then madara decided to use him as apart of his plans, to make sure nagato didnt fail...especially while zetsu was dragging obito's body down to
madara, obito's body might have been phasing in & out of zetsu's grasp and thats when madara realized
obito had a more unique power with his sharingan....
they said Minato was on a mission and it could have been trying to recover the 9tails form the raikage's ninja
unless thats when he saved kushina as a little girl:|
but zetsu is a weaker form of madara/hashi so they arent as potent nearly , but just enough to follow orders