Focusing on the cycle of political instability and development failure in Afghanistan, this research examines three main variables including ethnic divisions, external dependence, and legitimacy crisis as factors in this cycle. faults that are intertwined with internal political and security competitions and have prevented the creation of an inclusive and stable state. Also, historical and structural dependence on foreign support, whether in the form of direct interventions by world powers or in the form of dependence on financial and military aid, has weakened the country's independence of political decision-making and has led to the fragility of the state structure. The legitimacy crisis, as a complementary link in this cycle, is caused by the lack of transparent elections and the weakness of democratic institutions, which ultimately has led to citizens' distrust of the political system. The research method was conducted in a descriptive-analytical manner and data were collected from historical, political sources, and contemporary reports. The findings show that the combination of these three factors has trapped Afghanistan in a vicious cycle that is difficult to escape from, such that whenever there is room for development, ethnic divisions or foreign interventions have disrupted stability and exacerbated the legitimacy crisis. The results suggest that resolving the Afghan crisis depends only on redefining political legitimacy based on genuine citizen participation, reducing dependence on foreign support, and constructively managing ethnic diversity. Otherwise, the cycle of political instability will continue and the failure to progress on the path to development will continue.