The way a class action lawsuit works is this:
You, Big Business Co, do something that injures a bunch of people for a small amount. A lawyer files a lawsuit on behalf of a purported class - i.e. "Everyone Bezos Hurt vs. Amazon". There's a whole thing about class certification and other things I don't have time to get into, but let's say the judge agrees that this is a class whose harms can be adjudicated together.
At some point, if you actually have a claim, Amazon wants to pay money for it to go away. This is an accepted part of the legal system, because US courts are adversarial courts[0]. The judge is just the referee. That means that if the plaintiff and defendant agree to take their business elsewhere, the judge can't get involved and continue to prosecute a dead case[1].
First problem: lawyers don't work for free. In fact, pretty much all of them are in massive amounts of student debt until their 40s and 50s, because their ability to command insane amounts of money for their services is priced into the cost of their education. Normally, a lawyer either gets paid by their client, or the client agrees to the lawyer taking a percentage cut of the damage award if one were to exist. Problem is, there's no client yet - we're suing on behalf of an abstract group of people that may or may not want to be involved in the case.
Second problem: we don't know who's a member of the class, or even how many people are a member of it. Settlement agreements typically involve cash payments of a fixed amount. You have to divvy that fixed amount up to an unknown number of people.
So as a result every class action settlement works like this: first, the lawyer gets a cut of the settlement, then the class splits it up however many ways. People have to respond to a settlement offer in order to be included in the class. If more people sign up than we have money for, however, then the class members are diluted. Amazon's liability does not increase just because they harmed more people than they thought.
This is, effectively, a weird kind of double protection racket, in which the person shaking Amazon down for money is also taking money from Amazon to shake them down for less so the mob (us) doesn't get as much. All of it is enabled by fairly understandable and straightforward rules being chained together to arrive at a terrible result.
[0] The opposite of this is inquisitorial courts. Inquisitorial as in NOBODY EXPECTS THE SPANISH INQUISITION!
[1] There are certain situations in which a judge can object to a settlement that is unfair to the class, but they can't outright demand the case be brought to trial.