Romiosini,
Bishops and priests who had an orthodox confession, but who were nevertheless united through communion with Arianism, are known as Arians. There were Arian monasteries who had an orthodox confession of faith (and the Arians were happy to let them be until such time as they had the power to do something about them), but because they were under Arian bishops they were and are known as Arians.
Their monasteries no doubt, looked much much more Orthodox than this picture you are showing. In fact, if one could see those pictures today and compare them to the pictures they might see of St. Athanasios worshipping in homes, most would certainly conclude the Arians were Orthodox and St. Athanasios was, well, something strange.
But this is just it. People are impressed with appearances, numbers, and are seduced by the impression it brings.