According to Swimswam, it is the corona situation in Japan that is the reason for the championship being postponed.
The World Championships in Fukuoka should have been held this summer, but since the Olympics in Tokyo were postponed for a year, the swimming championships also had to be postponed to the future.
Swimswam also states that the WC 2023, which is scheduled to take place in Doha in November, will be moved forward by two months, to January 2024. If this happens, it will be the first time that a swim WC takes place in the same year as the Olympics.
The Olympics take place in Paris in the summer.