Moon Goddess had been born on the Moon, so she didn't know much about Earth. All she could see were some of the major things that had happened on Earth. It had to be a sufficiently large commotion for her to see a thing or two.
Just like how the ship had flown out of thin air back then, Moon Goddess could see such a huge matter clearly from the Moon.
Originally, the battle between Chiyou and Yellow Emperor wasn't enough for the Moon Goddess to observe. However, a huge meteorite had slammed into Earth. If Earth had been hit, most of the creatures would have been wiped out.
Moon Goddess didn't know what the experts on Earth had done. However, Chiyou had worn the Weapon Lord Armor and destroyed the meteorite.