Many Catholic churches face east because of the custom of praying in that direction, which has roots in the early Christian practice of praying towards the Mount of Olives in Jerusalem. The earliest Christians believed the Mount of Olives was the location of the Second Coming of Christ, and they would pray towards it.
Jews in the Old Testament would pray facing the temple in Jerusalem, which was considered the home of God.
The rising sun is connected to the glory of the returning Son, and this idea is found in Scripture.
The prophet Zacharias referred to Christ as “the Orient is his name”. The custom of facing east became general throughout Christendom, and the word “orientation” comes from the Latin word orient, which means “east”. Not all Catholic churches face east, and St. Peter’s is a notable exception, however, he altar in St. Peter’s Basilica is made from a single block of marble from the Forum of Nerva and faces east, as do altars in early Christian churches.