Why was Orson Welles’s film It’s All True left unfinished?

Orson Welles’s film It’s All True was left unfinished because the studio, RKO, canceled the project midway through production while Welles was in South America filming. This cancellation left Welles stranded in Rio de Janeiro.1

The project was intended to be an anthology of three short films: "The Story of Samba (Carnaval)," "My Friend Bonito," and "Four Men on a Raft". While the film was never released in its original form, much of the footage from "Four Men on a Raft" was later assembled and released in 1993 as part of the documentary It’s All True: Based on an Unfinished Film by Orson Welles.1