
Originally Posted by
The Super Long Interview with Kazuki Takahashi-sensei
After getting the Millennium Eye in Egypt, Pegasus spontaneously decided to make the cards.
[...]
However, the Millennium Items have always had a quality to attract to
one another. Pegasus, guided by that quality, resurrected the cards that
would prompt the Items to assemble. This was, rather than the
Millennium Eye giving him a revelation, he had been brainwashed washed
by the Millennium Eye. It's also possible to think that, in the end, the
cards were created by him, or, that, they were made to be made by the
Millennium Eye. Since he was originally good at painting, he may have been chosen by the Millennium Eye.