Plus keep in mind that 2 mountain runner types placed 2nd and 5th I believe against some pretty tough (2:08 to 2:10 marathon) runners. So they didn't exactly get destroyed, and as has been mentioned several times already, this wasn't really a proper mountain race.
There are clearly some people who are better suited to certain types of "extreme" running. I observed it first-hand in high school. I was mediocre at XC (17:52 PR) and was usually #7 man on the team. Our top 3 were what I considered very good at the time (#1 ran 15:49 on legit course) so naturally I was never anywhere near them in workouts. Never. But then one day coach had us do stadium steps for about 20 or 30 minutes, and I not only was ahead of the top runner, but I wasn't even trying that hard. The next day I was right back to my usual place in the pack and thought maybe it was just some weird fluke, until a couple of weeks later we went back and did the same workout, and the exact same thing happened.
One odd thing to mention is that I was never particularly good on regular hilly courses. I would just hold my place most of the time on the uphills. Even when the team did regular hill repeats on the roads I finished in my usual place. But later in life I had the opportunity to run some hill climb races at ski resorts and such, plus Pike's Peak a couple of times, and I did find that when the hills got really long and steep, I could beat people who were generally quite a bit faster. Maybe it has something to do with physique--I'm very bottom-heavy, with disproportionately large quad muscles.