Father Rodney and the others didn't go back directly. Instead, they used some of the remaining Holy Words and Holy Oil to create a few temporary altars with small stones around them, arranging them in a specific pattern on the shore. This operation took quite some time, but it was for safety.
Jimmy's earlier words made Father Rodney realize there's something in the lake, though he couldn't tell if it was a Resentful Spirit or some other unknown entity. To prevent any unexpected events during their absence, they had to set up protection, not just for what they planned to do the next day, but also for everyone else's safety.
Once everything was dealt with, Jimmy and the others left the lakeside and departed from Ghost Lake with Nia and several police detectives.
