Complex sentence: In 1542 he became a Fellow of Magdalen College, but he left the same year, possibly because of a purge of evangelicals and/or because he, like John Foxe, were due to take holy orders which entailed a vow of celibacy.
Split into simpler sentences: In 1542 he became a Fellow of Magdalen College, but he left the same year. Crowley's departure may have been due to a purge of evangelicals and/or because he, like John Foxe, was due to take holy orders which entailed a vow of celibacy.