Knife fighting is something a lot of people don't really understand, both being the one with the knife and the one defending against someone with a knife.
Someone with a knife, whether they're trained or untrained, is one of the most dangerous people anyone can face. That's because it's very easy to flail a knife around and slash and stab people. Someone that attempts to grab the arm of an attacker with a knife will end up having that arm slashed several times and still not be able to grab that arm. That's because hands are the fastest moving parts of the body, so they're very hard to target and grab a hold of, especially in struggles like this. Instinctively, we flail our hands and arms around the moment we see anyone reaching for our arm.
Knives and all weapons are "force multipliers". One of the problems most people have in assessing their ability to deal with someone with a knife is that they often give too much weight to their own physical attributes in comparison with the attacker with a knife. If you're a man, 6 foot tall, and weigh 240 pounds, you might think you'll just be able to walk up and take that knife if the attacker is a woman, 5 foot tall, and weighs 120 pounds. You'll end up getting stabbed and slashed a dozen times before you get the knife. And yes, you can easily die from loss of blood due to this.
It doesn't really matter how big and strong someone is when they have a knife. How much deeper will a stab go if the attacker is 10 times stronger? Right, it goes just as deep no matter how strong that attacker is. Stabbing someone is really easy with a pointy knife.
As for slashing, how many more slashes can someone do who is stronger? It's about the same. They might be able to slash through clothing more easily, though. But chances are that a smaller, weaker knife wielder can do enough damage that you'll end up dead due to blood loss.
The scenario the original question posed involved multiple stabs first, followed by slashing the throat. And the victim in this case was still able to walk after getting stabbed. Here's the thing. Blood loss takes a minute or two before they begin to pass out. Being stabbed that many times assures that a major artery was hit.
And you may wonder how a weaker individual can get off 29 stabs without being stopped. The thing is, most people can easily pick up a knife and just start stabbing and slashing violently. It takes no training to do that. It's just instinctive. If you have a knife in your hand, and you're insane with anger and want the guy in front of you to die, you will probably be successful at it. But on the other side, the defender would have to be so amazingly skilled in knife defense to be able to avoid getting any damage. The best trained escrima / kali fighters can't even do it, so there's no chance an untrained person can.
You might be interested in my answer to another question on this subject: Targeting arteries / tendons in knife fights?
A typical defender who's barehanded against someone armed with a knife will not know how to deal with that situation, especially not quick enough. At no point should a defender engage a knife fighter directly in close range. They need to keep their distance and create obstacles to shield them while trying to run away. Or they need to use a gun. That is, if the attacker actually allows it. In most cases, someone with a knife isn't going to give you time to assess the situation and get some distance. Knife fights go down fast.
So imagine you're in an enclosed area like an apartment, and someone pulls out a knife on you. You won't even be able to process this mentally. The first stab will happen, and you'll be like, "What just happened?" You'll just be standing there. Then a dozen more stabs happen, and you're barely able to turn around and start walking away, trying to get to a room with a door you can use to shield yourself from them. That's what it's like.
In real life situations, a knife can come out without any warning. A guy in front of you seems aggravated and nervous, but he's minding his space and not acting in a confrontational way. Then he turns away a little, and when he turns back to face you, suddenly he's stabbing you. You won't even see the knife in his hand it happens so fast. And once again, that takes zero training on his part to know how to do that. Whereas for you to defend successfully against it, it would require a super-human level of skill. Nobody really can. If you survive, it's because of luck or because he didn't want to do the worst to you.
Knife fights are a martial artist's worst nightmare. Many martial arts teach a bunch of techniques to deal with people with knives, like knife disarms and such. Those techniques work in some cases where an attacker is just showing a knife and doesn't really want to use it. But they will not work in cases where someone really wants to kill you with their knife and has already started using it against you. The problem is that martial arts often leave out the second scenario and just concentrate on the first. That gives students a fatally false sense of confidence in their knife defending abilities.
Hope that helps.