Why would Moon say "why" in this context? As an exclamation, does the word "why" have another meaning?

Native speaker’s answer
Rebecca
"Why" can be used as an interjection to express surprise, hesitation, impatience and other strong emotions. It is not recommended to use it as an exclamation since exclamations can be used on their own, and using "Why!" on its own could be mistaken for a question. Ex: Why, that's the biggest fish I've ever seen! Ex: You're giving me a guitar? Why, that's the best gift anyone's ever given me!