Complex sentence: Eusebius succeeded Agapius, as Bishop of Caesarea soon after 313 and when the Council of Nicaea met in 325, Eusebius was prominent in its transactions.
Split into simpler sentences: Eusebius succeeded Agapius, as Bishop of Caesarea soon after 313. When the Council of Nicaea met in 325, Eusebius was prominent in its transactions.