I guess they didn't have enough ressources to make the rest.
Who is the "witch in noir" ? What was the source of the Evils ? What was the reaction of the Rectory when she came back ? Could we have seen a witch transform into an Evil if we had more chapters ? Did they test this ring properties before ? Could they have tested it on a transforming witch and saved her ? There were a lot of opportunities to make more interesting chapters.
The ending was rushed and convenient, too bad because the story was quite good.