Fully agree with Anigrams.
In addition to what he has said, the lawsuit is against the users and not Fiverr. Fiverr Policy clearly states that if the user violates the Fiverr Policy, Fiverr will not defend them, so the users are on their own.
Please also note that Unjust Enrichment has multiple criminal clauses that can be invoked by prosecutors (if they take notice of these activities and decide to pursue the case independently) which include Wire Fraud, Racketeering and other sub-clauses.
Amazon reviews can be fake but Amazon has no way of proving that they are paid for fake reviews. This is a case of paid for fake reviews, which is treated as economic interference with those who are ethically trying to sell their products.
Paypal will also provide all the names promptly under the Civil Subpoena and then Amazon may use to pursue 2nd Tier cases in the country of origin of the named sellers. Amazon may settle the case on case by case with each seller basis how the named parties respond. Last time Amazon settled such case, the settlement payments were anywhere from between 7500 USD to 3.5 M USD each party plus legal costs.