Answer:
They thought it would help get rid of the plague.
Step-by-step explanation:
The knowledge that people have regarding how diseases spread at that time was extremely limited. They have no idea where the plague was originated, how was it spread, and what should they do to handle it.
This make people extremely afraid to be in close proximity to the infected people, let alone touching them. Because of this, a lot of bodies were left lying on the ground without being buried.
As a solution, many of them decided to just burn down the whole village.
They hope that the fire will somehow eliminate the cause of the plague and it also get rid of the decayed bodies off the street.