I can't agree that the mindset is irrelevant, whatever importance skill does or doesn't have. I've been training martial arts for over a decade, and I've seen mindset make a real difference in person, and that's not even in life or death struggles. In fact, I'd go so far as to argue that skill/mindset are inseparable to some extent.
But really, what I'm specifically saying is 2 things: that we can't understand their mindset, however much skill comes into play, and that we don't know anything about their skills, either. That's a historical black hole for us. Look at all the assumptions that have been made in this thread- that they just killed babies and starving peasants, untrained people, that they had no formal hand-to-hand method, that they relied more on psychological, fear-inspiring techniques, than combat skill, etc. This is really all wild speculation based on media stereotypes. Christianity and other historical forces wiped out almost everything we would actually use to get a real perspective on them with respect to the specifics of how they fought.
And I also have to disagree with the comparison between a Taliban fighter and a viking. They're militants with some training in modern warfare and guerrilla tactics. I can see that there would be some crossover, but I don't think one maps neatly onto the other. The Taliban culture may have precedents in Afghanistan's older warrior societies, but it's still not a culture where people are killing from childhood on (one of the few things we do know about vikings is that they did do that) even if for some of them, things are indeed moving in that direction, and also where this kind of fighting is the primary method of settling disputes, establishing social hierarchies, etc. They also know that they are outmatched when it comes to arms, etc, against an army like the one you were in.