Your sense of history is lacking again. St. Athanasius was out of favor of the courts of CONSTANTINOPLE, not Rome. The capital of the Roman Empire was NOT in Rome. The Emperor lived in the Eastern half of the Empire. Thus, Athanasius was at the mercy of political infighting in Constantinople. Thus, he APPEALED to the Bishop of Rome, the Pope, to aid him. The Pope highly regarded the future saint and backed him up vs. Arianism and those bishops who were Arian.
Regards
But Constantine did favor Arius in this dispute, did he not?