He advertised his NFT experiment on a forum [1] (a French equivalent of 4chan) and it went viral there. Some people bought it as a joke (knowing it was worthless). Nothing prove he didn't buy the tokens himself to hype it.
[0] https://opensea.io/collection/cyberalienz [1] https://www.jeuxvideo.com/forums/0-3011927-0-1-0-1-0-finance...