It might be worth asking the guests what they feel should have been included in the listing that would have made it five star. But really there is no logic.
I was recently given my first ever 3 star rating for value 😞
I offer guests a double room with expensive new mattress and bed, newly refurbished with new carpet and newly repainted, a wide selection of teas and coffees, bathrobes, quality toiletries, full access to a kitchen with oils, herbs, spices, coffee maker, food processor etc.
A living/dining room with books, games etc
Courtyard garden
1.5 bathrooms
For £30 a night plus one off token £5 cleaning fee. (plus Airbnb fee).
I was gobsmacked that she gave me 3 star for value.