How did the Este family gain political influence in Ferrara?

The House of Este first established political importance in Ferrara during the lifetime of Obizzo I (died 1193), when his son, Azzo V, married the heiress of one of the city's two rival families. While Azzo VI later acquired significant authority, the family's position remained precarious until 1240, when Azzo VII returned to power by aligning with the Guelf league supported by Pope Gregory IX.1

This alliance marked the true beginning of Este rule in the city. In 1264, the people of Ferrara, under pressure from Guelf strength, named Azzo VII’s heir, Obizzo II, as perpetual lord. The family subsequently solidified its control by expanding its influence into neighboring territories, such as Modena and Reggio, and constructing the Este Castle as a symbol of their power and defense.12