Why does the Moon look huge near the horizon?

Answer: Your brain compares it with trees and buildings

Earth's air acts like a giant magnifier — Not really. Atmospheric effects can distort the Moon, but they are not what makes it look dramatically bigger.

The Moon is physically closer at moonrise — Nope. The Moon is not suddenly much closer at moonrise. The effect is mostly in your perception.

Your brain compares it with trees and buildings ✓ — Correct! This is the moon illusion. Near the horizon, your brain compares the Moon with familiar foreground objects, so it feels much larger than it really is.