1983, Changzhou, a new city (there are many in China), was listed as a key development city. At that time, in order to optimize the economic prosperity of the Shanghai-Nanjing-Hangzhou triangle, Jiangsu Province focused on supporting neighboring cities like Changzhou, so the Jintan Wujin you mentioned was a very poor place and was included in Changzhou.

But Changzhou also wanted to be included in Danyang, but Zhenjiang at that time was not Zhenjiang today, which had a great influence. Zhenjiang authorities did not agree to include Danyang, so Changzhou did not get Danyang.

At that time, Changzhou had been squeezed into the first-tier cities in southern Jiangsu after the rapid development of tax exemption and low taxes in those years, and Zhenjiang became the last city in southern Jiangsu. You can't infer the policy decisions of that year from the current prosperity.