The sage just wrote the history of his mom on the tablet, and gave it's consequences. Madara interpreted IT as a good thing.
Also The moon didn't open up his eye. The moon is several hundred thousand miles away from earth, Madara only flew a few KM into the air, in the grand scheme of things, it didn't bring him any closer to the moon. If the eye could be activated by being several hundred thousand miles away minus a couple miles, then it doesn't matter where he is standing. More than anything, it's probably just the moonlight, which would've reached him if he was on the ground anyway