They didn’t receive what they paid for. That’s the point.
They bought what were presented as quality books that were highly popular and well reviewed. What they received was utter crap that was created as part of a multi-million dollar scam, which used shill fake accounts and shill buyers to falsely inflate purchase numbers and popularity, and used scam reviews. The scheme was against the Amazon TOS, and was designed from the ground up. Buyers did not get what they paid for.