Then the question becomes, why can a 3 month boxer beat a 5 year tkd guy in this ruleset? (just pulling an example out of thin air)
I have not seen it happen, so I have to answer in principle.
In principle, such things can be explained by the rules used. The one whom the rules fit the best, has a significant advantage that can exceed the advantage of longer training.
Of course, I mean both the rules of the match in questions, and the rules that each combattant is most experienced with.
One interesting consequence of it is that the martial art with the less limiting rules should benefit. Aikido is way up there