Why did Otto Preminger take over as director of Laura in 1944?

Otto Preminger originally intended to both produce and direct the film Laura (1944), having secured the rights to the underlying novel by Vera Caspary. However, studio mogul Darryl F. Zanuck initially assigned Rouben Mamoulian to direct the project while limiting Preminger to a producing role.12

Preminger took over as director after Zanuck became dissatisfied with the early footage produced by Mamoulian. Furthermore, conflicts had developed between the cast and Mamoulian. Consequently, Zanuck fired Mamoulian, scrapped his footage, and reinstated Preminger to direct the film.12