Why is Zhenjiang dialect so similar to Huaiyin dialect?

Due to the special geographical location of Zhenjiang, there are many dialects, with different customs in ten miles and different sounds in eight miles. Zhenjiang is also a watershed of dialects, between Huaiyang dialect in northern Jiangsu and Wu dialect in southern Jiangsu (for example, Danyang in Zhenjiang speaks Wu dialect, but people in Zhenjiang can't understand it). I am from the suburb of Zhenjiang, and we are different from Zhenjiang people in many ways, a bit like Wu dialect.

Another problem is that Zhenjiang has always been a city of migrants. From the Three Kingdoms, northerners moved here in the Tang and Song Dynasties, and more in the Republic of China. Due to the war, many Huaiyin people in northern Anhui fled here and later settled here, thus changing the original local language of Zhenjiang. Since then, the language is more inclined to the north, and we can feel the similarity of the language.

For example, my grandfather is from Huaiyin, so I have a quarter of Huai 'an descent, but I can't speak Huai 'an dialect.