Then you are free to sue whoever you think is violating your copyright. That's one of Serpapi's defenses: the owner of the copyright needs to sue, not a non-exclusive licensee of the copyright (Reddit).
This is a great legal defense, but if they are trying to make themselves seen as though they are fighting for the rights of the users and aren't doing the literal same thing that Reddit is doing, that is disingenious.
I wonder if any lawyers could weigh in here. Does this admission that they know the data is the user's make a class-action against SerpApi or whatever a slam-dunk? They're practically publishing their own admission of guilt!