Her extraordinary stage performance should not be attributed to sheer fluke only.

Event : a thing that happens or takes place, especially one of importance.
Accidence : the part of grammar that deals with the inflections of words.
Chance : the occurrence of events in the absence of any obvious intention or cause.
Meeting : an assembly of people for a particular purpose, especially for formal discussion.
Fluke : an unlikely chance occurrence, especially a surprising piece of luck.

Synonym of Fluke is Chance