How Madara absorbed chakra.
So, I did a bit of research on Naruto wikia and found an article on chakra absorption:
Chakra Absorption Techniques (チャクラ吸引術, Chakura Kyūin Jutsu; English TV "Chakra Absorption Jutsu") are techniques that allow the user to absorb another individual's chakra. They are typically used to absorb chakra from an opponent and add it to the user's own chakra reserves, allowing them to utilise it as if it were their own, while simultaneously exhausting the opponent's physical energy and limiting the techniques that they can perform.
Some ninja, such as Yoroi Akadō, Jirōbō, Kisame Hoshigaki and Orochimaru are able to use this technique by merely coming into contact with an opponent."
I think Madara too absorbed chakra from that fodder ninja in the same way :