Answer:
Luck or More difficult task
Explanation:
It is possible that the winner of the award was not actually better than other rookies instead may have had an element of luck and therefore could not reciprocate the performance the following year. It is also possible that because the person won the award, the person was given greater task base on the performance and it make them perform less. It is also possible the person cannot handle fame and it got into the person head and becomes confident in their abilities that the person stop improving and advancing their skills.