Amazon calculates a product's star ratings based on a machine learned model instead of a raw data average. The model takes into account factors including the age of a rating, whether the ratings are from verified purchasers and factors that establish reviewer trustworthiness.
This is by far the worst product I've ever used. Forget about this being a "perfume", it's worse than a cheap deo. Smells terrible. If you're buying this, you might as well flush your money down the toilet.