alright guys, it's my first time posting but i think that i've noticed something really important so yeah, hear me out.
Hypothesis: MADARA USES OBITO'S BODY
1) Obito is the only person left with the sharingan besides sasuke and itachi.
2) Madara's mask only reveals one RIGHT EYE sharingan.
3) Before obito supposedly died, he transferred one sharingan to kakashi's LEFT EYE.
4) Therefore, it only makes sense that madara/tobi's mask reveals only his RIGHT EYE because he has obito's body - his LEFT EYE is GONE, GIVEN TO KAKASHI.