Traditional command structure and social hierarchy (from Wookieepedia):
Mandalorian clan structure was like a pyramid, with the ruler or Mand'alor at the top and the Protectors enforcing their rule. Below them were the political factions known as Houses, made up of family Clans. For example, House Vizsla was comprised of Clan Vizsla and its allies like Clan Wren.
However, by the Clone Wars, Mandalore had become mostly pacifist, and was led by Duchess Satine Kryze and the New Mandalorians, who appear to have a fairly light hiarchy, with the Duchess being the only noble mentioned.
In the final year of the The Clone Wars, The Shadow Collective (made up of forces from Death Watch, Black Sun, the Pyke Syndicate, the Hutt Clan, and the Nightbrothers and led by Maul) successfully enacted a coup and took over Mandalore. Maul ruled the planet at that point.
Maul was later captured by Darth Sidious, causing his hold on Mandalore to collapse, and allowing the Empire to take over.