In Tangshan, why is the accent of Luanxian County in the south of Laoting basically the same as that of other counties?

I don't agree to go upstairs Changli, referred to as Changle for short, has similar accents in Luannan, Luanxian and Laoting. They refer to Changli, Luanxian, Luannan, Laoting, Tanghai and other counties in the alluvial plain in the lower reaches of Luanhe River. It turns out that there are only Feng Run, Yutian, Zunhua, Qian 'an, Changli, Luanxian and Laoting counties in eastern Hebei, among which Changluanle County is adjacent, with almost the same dialect customs, prosperous culture and education, and talented people, which gave birth to Pingju and Laoting drums. The area is surrounded by mountains and seas, and the land and water transportation of Bohai Sea and Luanhe River is very convenient, with a strong business atmosphere. At the end of the Qing Dynasty and the beginning of the Republic of China, the Changluan Music Business Group was once prominent, among which Laoting people were the most outstanding. Before the rise of Tangshan industry, Luanzhou Town was the economic center of eastern Hebei. The dialect here has outstanding characteristics, extensive external contacts, great influence and impressive. So many people call Chang Luan musician Lao Yi. Of course, the name was later expanded to cover all Tangshan people. Although Changli County is now under the jurisdiction of Qinhuangdao, there are obvious differences between Changli Qinhuangdao and other counties, but it has many similarities with Luanxian County, Laoting and Luannan, and has a strong sense of identity. The formation of dialects takes a long time, not a decade or two.