With the benefit of hindsight, this makes sense and is an exciting entry in the saga. At the time, I’m sure I would have been right there with my pitchfork and torch, ready to burn the theater down saying, “what the hell what was that?”
This is a slasher film. Don’t overthink it. No need for Druids and Stonehenge and curses. Just Michael Myers, his knife, and some unsuspecting teenagers.
It’s one of those historical films you have to watch once, but will probably never revisit.