McDonalds already had multiple successful suits against them about this very thing.
The lady in question got incredibly serious burns on her legs.
She originally sued only for medical expenses, and McDonalds wasn't interested in settling.
The award was later reduced.
If the answer to bad corporate behaviour is not regulation, but rather lawsuits, then that lawsuit perfectly encapsulated the series of legal escalations necessary to deal with a bad corporate actor, that has been alerted of a problem in their product, and refuses to resolve it.