Why did they decide the new government should be a democracy

Because it has a number of built-in mechanisms for promoting fairness and participation

Explanation:

According to American political scientist, democracy consists of some key elements.

A political system for choosing and replacing the government through free and fair elections

The active participation of the people, as citizens, in politics and civic life.

Protection of the human rights of all citizens.

Democracy promotes participation. Even poor people without formal education, living in disadvantaged neighborhoods, and little authority can play a significant role. It's self-adjusting. A democracy allows the most pertinent issues to rise to the top.

Democracy is far from perfect, but when it comes to running a government, it has a number of built-in mechanisms for promoting fairness and participation