Why did Empress Agnes support Cadalus of Parma as Antipope Honorius II?

Empress Agnes supported Cadalus of Parma as the antipope Honorius II primarily due to the deteriorating relationship between the German court and the reform-minded papacy following the death of her husband, Emperor Henry III.12

Under Henry III, the German crown had maintained significant control over papal elections and church affairs. However, after his death in 1056, the papacy began asserting its independence through new election procedures and a defensive alliance with the Normans in southern Italy, whom the German court viewed as usurpers. These developments, combined with disciplinary actions taken by Pope Nicholas II against German bishops, created severe tension.2

In response to these strains, Agnes—acting without the guidance of a permanent council—entered into an alliance with Italian opponents of church reform. By backing Cadalus, she sought to challenge Alexander II, who had been elected by the reformers without imperial sanction. Ultimately, her support proved ineffective, and she lost the regency in 1062 following a conspiracy of princes led by Archbishop Anno of Cologne, who subsequently recognized Alexander II.21