Why did Nikon disqualify a microscopy video winner over AI rules?

Nikon disqualified the winner of its Small World in Motion video competition after determining that artificial intelligence was used in violation of the contest rules [1]. The original winner, Ning Xu of Tsinghua University in China, had created a video showcasing cilia beating in the airways of a child with a rare respiratory condition, but the use of AI breached the competition's requirements [1].