Well there are a few factors there, which we have to consider in the context of this being filed in the USA.
The first one is that there is sizable precedent for people with such injuries to win such outrageous cases. Yes, I know some anecdotes are merely myths, but in other cases significant handouts have been made. If it was a trial by jury, the odds can be worse. I'm not saying QF had no chance, or even a bad chance of defending itself, but the chance of failure shouldn't be discounted even though we may regard (with common sense) this as an open-shut case. And should the woman have won the case she would have been awarded punitive damages in addition to whatever was awarded for the case itself. That can amount to a lot (given that the case also dragged on), and QF would've had to weigh this in on the risk analysis (i.e. the 'potential consequences' factor).
It does beg to reason how this case dragged on for one year.
The second factor, and probably more applicable one, is even though QF and the woman came to a settlement, we don't know how much this was. The idea here of course is to 'shut her up' and minimise the risk of any further potential damage (not to her ears!); given that the case has gone on for so long, perhaps QF might have taken this as some sort of a signal that they had a good chance of losing the case (whether rightly or wrongly).
Of course, realised that QF probably has the muscle to hire a fairly decent legal team to help them, but so there.