Complex sentence: Attracted by his learning and sanctity, many local clergy and laity entered into communion with the Catholic Church, forming an Ethiopic-Rite Catholic community under the care of the Apostolic Vicariate of Abyssinia, which had its headquarters at Keren.
Split into simpler sentences: Attracted by his learning and sanctity, many local clergy and laity entered into communion with the Catholic Church. They established an Ethiopic-Rite Catholic community under the care of the Apostolic Vicariate of Abyssinia, which had its headquarters at Keren.