Why does Jiande in Hangzhou sound like Shangrao in Jiangxi?

Many Jiande immigrants came from Shangrao, Jiangxi, and now we still speak Guangfeng dialect in Shangrao, Jiangxi. Many people speak Nanfeng dialect. It may be that a large number of immigrants came to western Zhejiang in the late Qing Dynasty. When I asked my father, I couldn't tell the specific reason. Not long ago. My grandfather was born in Zhejiang, 1904. My grandfather's father (Taigong) was an immigrant and his mother (Taipo) married to Jiande, Zhejiang, so it took about a hundred years.