Final answer:
China not becoming an industrial power in the nineteenth century had no effect on the ukulele's twentieth-century popularity, which grew due to other factors like affordability and the appeal of Hawaiian music.
Step-by-step explanation:
The ukulele's popularity in the twentieth century was not influenced by China's industrial power, or lack thereof. The growth of this instrument's popularity was due to factors like its portability, affordability, the rise of Hawaiian music's popularity in the United States, and its association with popular entertainers.
In contrast, China not becoming an industrial power in the nineteenth century is a separate historical topic with a distinct set of contributing reasons, including possible political, social, and economic elements that are unrelated to the spread of the ukulele's popularity.