Okay, this is from Google AI, so take this with a grain of salt, but according to what I've read a company does not have to be in violation of any specific law to be targeted with a class action lawsuit. The minimum standard is that a company must be engaged in practices that have harmed a large number of people.
As well, it is not a prerequisite that the lawsuit be filed on behalf of a protected class unless discrimination is being alleged.
The key prerequisites regardless of protected class status are:
Numerosity: There must be a sufficient number of people affected to make individual lawsuits impractical.
Commonality: The class members must share common legal or factual claims that arise from the same event or course of conduct.
Typicality: The claims of the lead plaintiff (the person who initiates the lawsuit) must be typical of the claims of the rest of the class.
Adequacy of Representation: The lead plaintiff and their attorneys must be capable of fairly and adequately protecting the interests of the entire class.
As I said before, I'd say these actions taken by payment processors easily fit these criteria.