From scene 2, how does Sadiku try to convince Sidi to marry Baroka?

Sadiku tells Sidi that because her husband is old Sidi's marriage to Baroka will give her the opportunity of being the senior wife when the new Bale takes over. 

she marries Baroka because sadiku lies sidi that her husband had lost his manhood and this tempted her to go and laugh at him where she was being coughtup by baroka hence she marries her..

Saiduku try to convince sidi to be baroka wife by telling her that she will be his last wife and when the bale dies cidi will become the head wife of baroka successor.

why does sadiku try to convince sidi to marry baroka