Most of the debt was/is taken on to pay off political patrons, mostly characterized in the form of marked-up procurement. The IMF then turns off the tap as soon as a new regime takes power and decides to default. They don't stop making the maintenance payments because their rivals will pay off the patrons they can't and they would lose their support.

Their taxes are high because cronyism is pervasive and society is structure in a rigid caste-based hierarchy.