Renku became a Buddhist ritual. According to Gary L. Ebersole, the monks of Japan turned renku into a ritual. Through the course of a linked verse session, poets explore the transience of things. Realizing that nothing is permanent is a key step toward Buddhist enlightenment.
Ebersole's important essay, "The Buddhist Ritual Use of Linked Poetry in Medieval Japan," appears in The Eastern Buddhist 16.2 (1983): 50-71.