Like most things in life worth doing or having, randonneuring is about problem solving. That's all that's going on. The fitness part is not the big deal, as others have said. I can ride however far on a diet of 120 miles/week and nothing over 80 in one ride. I do ride hard, though. No, it's all about, I don't know, I suppose in the military it's called combat readiness. You know before you start that things are going to go wrong. That's the fun of it. It how you plan in advance for those things and then execute, even when you are sure you won't be thinking straight, that makes it work. It's a different mindset. It's not the racer mindset. It's a creative mindset.
Still, there is this goal thing going on. It isn't all touchy-feely. You want to win, and you don't want to die. Winning is defined as being alive and operational at the finish inside some time limit. That's the same race we all run and will all eventually lose. But for now, we can win a few.