Reasons why military leaders stage coup d'etat is when especially the civilian government is corrupt in many ways, when there is a lot of crisis in the country either religious, political and otherwise that the civilian government cannot handle, the military will stage in coup d'etat. Bellow are some other reasons;
1) Grievence: this theory explains that coups are caused by groups that mobilize to fight injustices committed by the state. After a long history of political, economic, and social injustices, many groups begin to start coups to stop the trend of injustice.
2) Greed: coups are started by groups of people who are tired of resource and other kinds of economic exploitation. Many leaders in Africa exploit their own land and people to extract valuable natural resource reserves, which eventually takes a toll on citizens. These citizens eventually start coups in hopes of attaining benefits of resources. (ex. Chad - many of Chad's coups have been started because of greed - stemming from exploitation of oil reserves in Chad)
3) Colonial Effect: many scholars argue that the cause of coups in Africa stems from colonialism. Colonialism implemented an ideology across Africa that justified the attainment of power through force. Scholars believe that this lasting effect has contributed to the cause of coups around Africa.