Complex sentence: The Aztecs believed that if sacrifices were not supplied for Tlaloc, rain would not come, their crops would not flourish, and leprosy and rheumatism, diseases caused by Tlaloc, would infest the village.
Split into simpler sentences: The Aztecs believed that if sacrifices were not supplied for Tlaloc, rain would not come and their crops would not flourish. Leprosy and rheumatism, diseases caused by Tlaloc, would infest the village.