Answer
The refusal of Zeami to acknowledge his nephew, Onnami, as his successor stemmed from a combination of factors. Onnami's lack of dedication to the art form, his pursuit of personal gain, and his failure to grasp the true essence of Noh drama contributed to Zeami's decision. Instead, Zeami chose his son-in-law, Zenchiku, as his heir, recognizing his commitment, talent, and profound understanding of the art.