Final answer:
The Congress of Vienna was considered a success because it restored peace and stability in Europe, established a balance of power among major European powers, and reinforced traditional beliefs and institutions.
Step-by-step explanation:
The Congress of Vienna is considered a success for several reasons. Firstly, it achieved its main goal of restoring peace and stability in Europe after the Napoleonic Wars. Secondly, it established a system of balance of power among the major European powers, which helped prevent further wars for nearly forty years. Lastly, the Congress of Vienna reaffirmed the legitimacy of overthrown monarchs and reinforced traditional beliefs and institutions, which was seen as a victory for conservative forces.