The British considered the rise of Khalid bin Barghash to the Sultan’s chair reason enough for war. Only six years after colonial wrangling during the scramble for Africa resulted in the Zanzibar archipelago becoming a British protectorate, the Sultan, Hamad bin Thuwaini, died.
Responsible for overseeing the day to day rule of the islands from his palaces in Stone Town, part of the protectorate deal required the Sultan’s rule to receive the blessing of the British consul. Khalid bin Barghash, the new Sultan, did not seek permission from the consul, and it seems unlikely he would have received it if he had. Hamud bin Muhammed was a far more appropriate choice from the British point of view.