Complex sentence: The St. Thomas Christians resentful over these acts later swore the Coonan Cross Oath, severing relations with the Catholic Church, and later came to be known as Jacobites.
Split into simpler sentences: The St. Thomas Christians resentful over these acts later swore the Coonan Cross Oath, severing relations with the Catholic Church. Those who did not come back to Catholic Church came to be known as Jacobites.