That was 700 complaints out of 171 BILLION customers over the course of 10 years. This is statistically nothing.
McDonald's judged that injuring people and pounding them with lawyers was more cost effective than customers not having hot coffee after they drove to the office.
McDonalds got off lightly.
It's not the volume of product sold that matters. It's the damages that one product can have in one specific case.
And besides, if they really had a case, they should have appealed rather than settled and then re-litigate it in the court of public opinion. Winning a case is always a stronger argument than trying to prove you were right afterwards.
Again, if they felt they would have won, they should have appealed.