Why were many monarchies overthrown during the 20th century?

During the 20th century, many monarchies were overthrown as they struggled to adapt to the rise of modern political ideologies and social pressures. The collapse of these regimes was driven by several key factors:

• Military Defeat and War: The devastation of World War I led directly to the fall of four major imperial dynasties—the Habsburgs of Austria-Hungary, the Hohenzollerns of Germany, the Romanovs of Russia, and the Ottoman Empire—as they were unable to survive the resulting military collapse and nationalist uprisings.123
• Social and Political Upheaval: Popular revolutions, such as those in Russia (1917) and China (1911), swept away monarchies that failed to address economic mismanagement, class conflict, and demands for representation.14
• Ideological Shifts: The spread of secularism, nationalism, and the concept of natural rights eroded the traditional legitimacy of "divine right" rule. Many 20th-century movements—whether anticolonial, nationalist, or Marxist—viewed monarchies as obsolete bastions of an old order responsible for corruption and social injustice.15
• Failure to Adapt: Monarchies that attempted to retain absolute power often failed to meet the needs of mass societies. In contrast, those that survived, such as in the United Kingdom and Denmark, did so by transitioning into constitutional monarchies where the monarch serves as a symbolic head of state rather than an active political ruler.53