One-word/phrase replacement for "made for the sake of being made"
The only ones that spring to mind are "for no apparent reason" (Collins: for no apparent reason) or "just because" (Collins: just because)
For example:
For no apparent reason, an eccentric billionaire has opened a restaurant on the Moon.
or
The eccentric billionaire decided to open a restaurant on the Moon, just because.
I don't think there is a word that literally means "made for the sake of being made", but on a more poetical level, the answer is:
ART