Complex sentence: In 1701, Father Louis de Montfort arrived in Poitiers, having been ordained a priest in June 1700, a young, highly idealistic priest who wanted to be the "champion of the poor", having been inspired as a teenager to preach to the poor.
Split into simpler sentences: In 1701, Father Louis de Montfort arrived in Poitiers, having been ordained a priest in June 1700. But in 1701 he was just a young, highly idealistic priest who wanted to be the "champion of the poor", having been inspired as a teenager to preach to the poor.