Why is the nano x called too the moon?
It's just part of their branding and marketing. But if you want a deeper answer from them, they have it on their official website.
To The Moon
5 years ago, 8 explorers from different origins, stood together with one common goal: bringing security & innovation to the cryptosphere. This is how Ledgers story started.
Our mission: Going to the moon.
Celebrate 5 years of crypto evolution with the new Ledger Nano X Limited Edition. With its specific engraving and one-of-a-kind box, buy yourself peace of mind.
Source:
https://shop.ledger.com/products/ledger-nano-x-to-the-moon-edition