Why did Florence’s political and cultural importance decline under the later Medici grand dukes?

The decline of Florence’s political and cultural importance under the later Medici grand dukes was driven by a shift toward authoritarian rule and the city’s transition into a minor player within the broader European balance of power.12

While the earlier Medici line had generally respected the republican ambitions of the Florentine people, the younger line—beginning with Cosimo I—established an absolute, military-backed rule. This transition resulted in several key factors that contributed to the city's decline:1

• Loss of Political Vitality: Constitutional forms and movements toward democratic government disappeared, and the city’s political autonomy was reduced as the dukes increasingly aligned themselves with foreign noble houses, particularly those in France.12
• Cultural Stagnation: Despite the family’s continued patronage of the arts and sciences, the city gradually dwindled as a premier center of creative artistic effort and scholarship compared to its earlier Renaissance peak.12
• Economic and Administrative Shifts: Some later rulers, such as Francis I, were criticized as despotic tax masters who negatively impacted the nation’s economy, though others, like Ferdinand I, briefly brought periods of stability and prosperity.1

Ultimately, by the time the grand ducal line ended in the 18th century, Florence had lost its status as a major independent power, leading modern scholars to refer to this era as the "forgotten centuries".2