Maybe $100B is too much for that particular infraction, but the idea of punitive damages has nothing to do with "fairness" or charging the real cost of the bad thing they did.

It's a deterrent. It says: "you did a really bad thing and I'm going to slap a huge fine on you so you think twice about doing it again". And "huge" has to scale with the entity paying the fine. It has to be an actual wound, not a papercut.