I think there are other reasons:
According to textual research, most of the royal family in the Tang Dynasty were from southern Fujian, and Li Bai was also full of Minnan dialect. Moreover, the poems and songs in the Tang Dynasty were developed. People who don't know Minnan can read Li Bai's poems in Minnan, and they will find that Li Bai's poems don't rhyme (read in Putonghua), but they can rhyme in Minnan, but this is only an expert's inference, but I think it can also be the reason why Minnan songs are developed.
In addition, Minnan is spoken in Taiwan Province Province and Mandarin is spoken in Hong Kong, and their return has attracted the attention of the whole country. At the same time, Hong Kong and Taiwan Province is an entertainment industry and its developed areas, and knows how to package and spread, so it is difficult for ordinary people to know that songs in other dialects are covered by Minnan-Cantonese.