The Sacklers would have to be complete morons(indeed, self-destructive morons) to have a settlement that did not include legal immunity, because otherwise they will get sued again and again and again. "Sure, we will give you this money and then someone else can file a lawsuit against us later" is not a stance you can reasonably expect out of anyone.
Instead, we ought to be asking "Why settle?" If you want to understand what's going on instead of feeding the outrage beast that the media has been nurturing in you for the last couple of decades, ask that question. And it's a good question: if it is such a slam-dunk, why did the government say, "Sure, we'll settle?"
Possible answers -- ones that someone could maybe do something about -- would include "Because the lawyers would eat up all of the money" and "There was a payoff to the right parties" and "The government wants the money now instead of later" (this one can be thrown out given the fine repayment period) and "the government feared losing its case." Feel free to add more.
It's a lot more constructive than being pointlessly angry.