It's tough to lie to a little kid, or one is possibly feeling too guilty at lying for so long, or tired of it all. Or maybe he thought nobody would pay attention. A key and telling snippet from a longer Q+A session with a child.
Our main man Buzz should have borrowed a line from the Grinch (Who Stole Christmas) and his encounter with Cindy Lou when caught out.
The moon and Apollo series missions / landings therein are just a small part of a MUCH greater fabrication and deceit on humanity. The rabbit hole goes deeper than just this facet. You can sort it all out if you're willing to spend the time. A future TSTDWYTKAD topic.
"Space may be the final frontier, but it's made in a Hollywood basement."
Red Hot Chili Peppers / Californication song (1999)