"I thought you were the moon in the sky,
But it turns out you were just a street light"
His initial impression of someone was that this person was a natural, down to earth, beautiful person. He then figures out that this person is actually a synthetic and fake person. Humans create street lights. This person was created, shaped and molded by others... and hasn't their own impression on anything. He is disappointed in this person, let down.
"I thought you were the moon in the sky, But it turns out you were just a street light"
His initial impression of someone was that this person was a natural, down to earth, beautiful person. He then figures out that this person is actually a synthetic and fake person. Humans create street lights. This person was created, shaped and molded by others... and hasn't their own impression on anything. He is disappointed in this person, let down.
That is my take on it anyhow.