Three elements are key for a fighter:
1. The person (or genetics, however you want to say it)
2. Training Methods
3. Style
Genetics and natural ability play a huge part in any sports or athletics. You may love a good Rudy story but the fact is someone who is 5'6" and 140 pounds will not be playing linebacker in the NFL. Similar in combat sports is someone who trains hard and has natural ability will have the edge over someone who trains hard but does not have natural ability. Just the way it goes.
"The hero and the coward both feel the same thing, but the hero projects his fear onto his opponent while the coward runs. 'Fear'. It's the same thing, but it's what you do with it that matters". -Cus D'Amato