However, it should be noted that the victory at the end is not real. Pennywise is not defeated. He is only trapped again. This is the same state he was in before. It is also how he exists during the movies. The finale makes one thing clear. Pennywise cannot be killed in normal ways. He exists outside normal time.

It: Welcome to Derry cast and crew unpack the big Pennywise reveal that explains why the show is telling the story in reverse.