Cassius Clay defeats Sonny Liston to win the world heavyweight boxing crown 53 years ago
When your on top like Liston you need to be ready for any and all contenders. Everyone knows your strengths and weaknesses and have lots of resources to analyze your style
When you are climbing like Clay/Ali all your focus is on the next rung. You haven't yet established a style. Your weaknesses and strengths are unknown or harder to identify.
The "underdog" has a serious advantage here.
Liston had freakish athletic proportions. Muhammad Ali always mentioned that Liston was the only guy he was truly afraid of fighting.
Liston didn't know his real age and was actually probably a few years older here, more likely early thirties. He had a reputation as a thug and so was denied chances at the championship for years.