It was (is) one of the most popular and successful air shows, attracting regular visitors from all over the World, with very large crowds (for a UK venue)
The COVID pandemic lead to cancellations for two years of course, and then, in 2021, there was a "disagreement" with the terms required by the Imperial War Museum, who run the Duxford site. There were hints hat this was due to the IWM wanting a large amount of money "up front", and the organisers (The Fighter Collection) decided to look for a new venue. This was to have been Sywell, although it never happened, and the first show since 2019 took place at Church Fenton in July this year.
It was then announced that the 2024 show would also be at Church Fenton, moving to its "traditional" date of the second weekend in July, as the only available date used this year clashed with the RIAT show and the Great Yorkshire Show, meaning lower attendances.
I don't know why the show has been cancelled, but hopefully the new Sywel show will be a good "replacement", and may even lead to "Legends" being held there in future years.