Decoys can be a fickle hunting tool. When they’re misplaced or look a bit too motionless, you're more likely to raise suspicion and spook your intended target than notch a tag.
The mountain lion in this video didn't seem at all deterred by that lack of life in this decoy. Cats are well known for causing a ruckus in the middle of the night, and this big kitty is certainly no exception.