Very few people have any understanding of the extent of the plaintiff's injuries in this case. The details were probably not considered suitable to write about in the press. However, because of how the coffee spill occurred, she experienced severe vaginal burns, severe enough to substantially interfere with her ability to have or enjoy sex, if able to ever have sex again at all.
There are a few other factors to bear in mind as well. First, when a plaintiff sues, the plaintiff is suing for injuries not simply up to that point, but also for all the medical consequences in the future and for all pain and suffering that will be endured for life. A plaintiff does not have a second bite at the apple. Thus an award is meant to compensate not only for what has already happened, but also to compensate for the future, for the rest of the plaintiff's life. A large award quite often reflects this principle in the law. Second, it is also possible that the plaintiff's spouse had part of this claim, for what is called "loss of consortium," which is a spouse's loss for what the plaintiff can no longer provide, in this case, a reasonable sex life.
Given that most of the public does not know all of this, it is not surprising that people find it appalling that someone got all of this money for a coffee spill. But this was not a "runaway jury" by any means. The plaintiff sustained severe injuries that were going to cause her a lifetime of pain and suffering, and if she had a spouse, that spouse had a legitimate claim, too.
I assume that you are asking about the case of Stella Liebeck, who spilled McDonald’s coffee on herself in 1992. If so, the reason she got damages from McDonald’s is because the jury ruled that the coffee was unreasonably hot and was therefore likely to cause injury.
The issue here was not whether McDonald’s caused Liebeck to spill the coffee on herself. Instead, the issue was whether McDonald’s was negligent in serving coffee that was so hot. In court, it came out that McDonald’s required that its coffee be kept at 180 to 190 degrees Fahrenheit. This is hot enough to cause severe burning (as happened to Liebeck, who required surgery for her burns) in a very few seconds. The jury ruled that McDonald’s was negligent to serve such hot coffee in a situation (small warning, flimsy Styrofoam cup) where it was quite possible that the coffee would spill on people.
Thus, this was not a case about a woman getting money because the coffee spilled. Instead, it was a case about the temperature of the coffee that was served in circumstances where spills were likely.