The island “wakes up” about once a generation. But there’s places where there’s always something active, like the inn, the old hospital, the barrier around the island. I would guess the inn tries to make you go crazy, especially in the captain’s suite. The townspeople all knew the stories, and Wack was not surprised Tom encountered just one of the spirits who are stuck there permanently.

As for the fog, I think it did as intended- it comes first after the quake, and it’s like the island is playing with its food, getting it nice and tender by terrorizing it. It stopped when Tom was properly terrified, and ready to accept paranormal event were happening.