When the public piles onto a popular favorite, the book's exposure on that side balloons and the line may move without any new sporting information - a purely risk-driven move. Distinguishing exposure-driven moves from information-driven ones (like a steam move) is a core skill in reading the market: one predicts nothing about the game; the other is the market getting smarter.
Exposure itself is internal to each book, but its fingerprints are visible in the feed: one book shading a number away from the market consensus while the anchor holds still is the classic signature. The movers view plus cross-book comparison makes those divergences easy to spot.