The alliance between Maul and Vizsla was never meant to last. Once in power, Vizsla betrays the Sith brothers, throwing them into prison. However, Maul uses Mandalorian culture against him. He escapes and challenges Vizsla to a for leadership of Mandalore—a challenge Mandalorian tradition states a warrior cannot refuse.
The Fall of Mandalore: A Look Back at The Clone Wars S5E15, " Shades of Reason " [S5E15] Target
It’s a chillingly effective piece of theater. By appearing as the planet's only true protectors, Vizsla easily secures the public's support, ousting Satine and installing himself as the new Prime Minister. The Ultimate Power Move: Maul vs. Vizsla The alliance between Maul and Vizsla was never meant to last
The resulting duel is one of the most cinematic in the series: Vizsla betrays the Sith brothers