No, the development of a country cannot depend solely on its politicians, because the hard work and ethics of its people are also important. The country needs hard workers with solid moral backgrounds in order to start businesses. Good citizens also make a country develop through their generosity to fellow citizens. The people matter in a country's development.
Many factors, beside the work of politicians, can help the development of a country. Of course, the people are the greatest asset. Natural resources can also be beneficial to a country's development. International efforts can also keep the peace in developing countries, and loans from foreign banks an organizations can help more than any single politician ever could.