Seems rather common with book reviews, but in general Amazon runs a very tight ship.
Wish all e marketers were as much of a pleasure to use.
I’m a big fan of Amazon. They are battling to run that tight ship. One author had something like 200 fake 5 star reviews removed over night, leaving 2 poor reviews by their lonely selves. The technical challenge/sheer volume of the problem overwhelms Amazon and the company has to rely on support from readers reporting suspicious reviews and the ability of Amazon to detect it. THey are always improving their technology to address this but the scammers are evolving too.