Debt crises in developing countries can happen because they can't pay back what they owe. This can be because the interest on loans is too high compared to the money they make, or they can't get the foreign money needed to pay back their debts on time. Most developing countries will likely owe more money in the future, and crises happen when they can't get new loans or don't want to refinance because it costs too much. If they think their own money might lose value, they might wait to refinance to avoid losing money.