Due to the nature of the divisions separated by weight classes in tournaments, strength plays a huge part in the outcome of matches. Assuming all things are equal skill-wise, the athlete who is stronger and better conditioned will most likely win.
But sometimes, even high level athletes develop a very strength dependent style. They are stronger than their opponents the majority of the time, and use that to their advantage (utilizing moves that may not normally work otherwise).
Assuming that they are indeed stronger than their opponents MOST of the time, they will indeed win MOST of their matches. However, it would be foolish to assume that someone more powerful won't come along. Case in point, this following match:
Rustam Chsiev vs Tom Malenksi.