To me, this would be the expected second step, for someone infringing on their trademark. Like if a person steals your car, then you confront them and try to strike a deal to prevent involvement of authorities. If you ignore that, I think it is reasonable to expect them to report you to the police, and you to get charged with theft.
I don't think they expect to actually get 15M from this suit. Honestly, it seems like they wanted to avoid the suit altogether, because of how it looks from a PR POV.
I’m not GP, but I can take a crack: A case against a limited liability corporation for infringing on a trademark is not like murdering someone and burning down their house because no one ends up dead and no houses are burned down, and it is an appealable judgement made by a court based in legal precedent.
The damages listed in a lawsuit have nothing at all to do with the reasonableness of the parties involved.
By the time a lawsuit is filed you are already deep into a civil dispute, and very few civil disputes ever go to trial. Filing a lawsuit at all is the nuclear option for when all reasonableness has already broken down. You only go to court as the nuclear option after both parties reach an impasse.
15M is almost certainly just a result of mathematically adding up the damages the law provides for. That's how going to court generally works -- your lawyer will ask the court for everything the law provides for. Then the court will decide what is reasonable to actually award. Going to court is very expensive, and it is why ~99% of cases settle before going to court.
