Arianism gained popularity particularly in the fourth century for several reasons. One dominating reason lies in the fact that it was the favored position by the Roman Empire. Secondly, it was more popular amongst the heathens and philosophers who rejected Christianity according to the Spirit or for cultural or personal reasons. Thirdly, Arianism appealed to the more rational mind. Christianity must be received by the spiritual faculties of the soul as well as the rational, and for those following idols, the spiritual sight was often dimmed, and so they could not properly understand. Finally, Arianism paraded as “an Angel of Light” and a disguised evil. We understand throughout the history of the world, Satan reappears continuously as an “Angel of Light” that appears to the masses. His defeat is always imminent though.
Arianism stood as the generally more favored position of the Roman Emperors of the fourth century beginning with the reign of Constantine the Great. Arianism continued in favor by the Roman government until its suppression by the Emperor Theodosius. As a result of this, Arians living in the Roman Empire tended to advance in office, rank, or position in the Roman Army and government. Meanwhile, Christians were sometimes badly persecuted throughout the entire fourth century. They had to flee in exile sometimes, their lives were in danger at times, and they had to endure many afflictions. Essentially, Christianity carried a Cross and the Arians did not.
Many philosophers and pagan peoples from the Roman and Hellenic cultures were more drawn towards Arianism than Christianity because there was less of a cultural divide with Arianism. Further, Arianism appealed to the lower rational mind. This fit within the mode of philosophy. Arianism also held the “spirit of the world” which was spiritually likened to Heathenism in this regard. In fact, many Heathens had formerly persecuted Christians before Christianity became legal, and so after the Edict of Milan, with the spread of Arianism, they simply persecuted the true Christians again.
Finally, in regards to the contrast of darkness and light between Arianism and Christianity, we know that the Great Deceiver has often tried to portray what is darkness as light throughout the history of the world. In the end, Arianism was a spiritual battle that played itself out for an entire century.