Disney’s “Strange World,” an animated adventure about a family of legendary explorers, is having trouble discovering a great deal of treasure. The well-reviewed film grossed a disappointing $800,000 in Tuesday previews, which likely means that initial estimates that “Strange World” would pull in between $30 million to $40 million over the five-day Thanksgiving holiday may prove to be overly optimistic. That all comes with important caveats. Animated fare doesn’t usually do explosive business in previews, with families usually seeking out earlier showings. That said, “Strange World’s” Tuesday preview number is less than the $1.5 million that Disney’s “Encanto” generated in...