In the future after a nuclear war has ravaged Earth, leaving the Martian colonies on their own and without support...
Mars falls under the attacks of local militias, fragmenting. That is until some brave individual, their first empress to be, through some happenstance leads the broken Martian people, unites them, and sets them on the path to peace. After a long fought conflict, roaming bands of fighters, terrorists and bandits driven back, a united Mars now is on the way to crowning this girl.
This element is in the background of a story I'm working on. In the beginning the Martian colonies were multinational and administered by each nation until the war. The Empress to be was a symbol of the fight and rebellion, beloved by the people. But she didn't seek to be anything more than a fighter.
By the present in this universe the Martians are definitely a nearly absolute monarchy.
The question is: why would they be willing and all set to bring about a new monarchy?
I'm very,very sorry about last time. I'll rephrase the question and try to keep the answers relevant.
The monarchy is constitutional at first and then progresses closer to absolute.
Under what conditions could a Martian people or new government replace their old government with a monarchy?