the.com/red herring

means A fact or clue deliberately (or accidentally) introduced to distract from the real issue or lead reasoning astray.

from The literal red herring is a herring smoked until it turns dark and pungent — strong-smelling enough, the story goes, to drag a hunting dog off a scent if dragged across a trail. That training-and-hunting image is real, but the famous tale of escaped prisoners or fox-hunt saboteurs using smoked fish to throw off hounds is likely a 19th-century embellishment. The phrase actually took off through a journalist's anecdote about using the fish to illustrate a point about misdirection, and it stuck as shorthand for any deliberate (or incidental) distraction from the real trail.