Complex sentence: According to them, Ulfilas was an orthodox Christian for most of his early life and converted to Ariannism only around 360 because of political pressure from the pro-Arian ecclesiastical and governmental powers.
Split into simpler sentences: According to them, Ulfilas was an orthodox Christian for most of his early life. He was only converted to Arianism somewhere around 360, and then only because of political pressure from the pro-Arian ecclesiastical and governmental powers.