Why did the catholic church introduce tropes?
to convey to the common people the mysterious ways in which fate worked
to teach morals by dramatizing the lives of saints and church leaders
to increase the common people's interest in and understanding of religious ideas
to popularize the classical language of latin among the people

First of all, trope is a figurative language using images, words or phrases to convey the creative work. Medieval texts used the rhetoric in liturgy. The main reason is to teach morals by dramatizing the lives of saints and church leaders. There is a ritual chant in Judaism called trope which does not have to be mixed with this.

we need the passage first