Complex sentence: The best-known form of liberation theology is that which developed within the Catholic Church in Latin America in the 1950s and 1960s, arising principally as a moral reaction to the poverty and social injustice in the region.
Split into simpler sentences: The best-known form of liberation theology is that which developed in Latin America in the 1950s. Liberation theology arose principally as a moral reaction to the poverty and social injustice in the region.