Either that or they were aware of what they were doing and left the extreme irony of what they chose to repeat as a kind of Easter egg for anyone familiar with the source.

Just kidding, they're lazy.

Pieces of art are repurposed all the time, I am sure Nietzsche took it from somebody living even further back in the past.

By that logic Nietzsche was also a lazy bum.

https://wikipedia.org/wiki/Eternal_return