Why did supporters of pagan Roman cults rally around Eugenius?

Supporters of pagan Roman cults rallied around the usurper Eugenius because they sought to preserve and restore traditional pagan religions within the empire, which were increasingly threatened by the policies of Theodosius I.12

Theodosius had taken aggressive steps to establish Christianity as the dominant faith, including issuing stringent edicts in 391 and 392 that completely prohibited the worship of pagan gods. By contrast, the regime of Eugenius—installed by the general Arbogast—offered a political vehicle for the pagan aristocracy of the Senate to challenge these restrictions.12

Consequently, the conflict between Theodosius and Eugenius became a decisive struggle over whether paganism would continue to be tolerated alongside Christianity in the Roman Empire. Led by figures such as Nicomachus Flavianus, those striving to maintain the old cults aligned themselves with Eugenius in a final, unsuccessful attempt to reverse the religious transformation of the state.12