What is the most fundamental reason for the decline of Northeast China?

In the early days of the founding of the People's Republic of China, the northeast economy reached more than 90% of the country, especially the part outside the customs. The main reasons for the decline of Northeast China are war, the victorious Sino-US War to Resist US Aggression and Aid Korea, huge war equipment funds, arrears of Russian loans, inability to pay debts, taking equipment from Northeast China and paying debts with grain from all over the country, hollowing out the Northeast economy, because most of the special economy in Northeast China is state-owned enterprises, and state-owned workers are laid off behind. People who have lost their jobs and no income choose to leave the Northeast. Later, the collapse of Hainan's real estate market has led to the situation that Northeasters moved to Hainan. If this battle is lost, then the Korean peninsula will be controlled by the United States, and the northeast region will also be put on alert. The original equipment should also be taken away and transferred to the economic center. Personally, I think this battle destroyed the Northeast. After all, the family planning behind the guns has further affected the development of Northeast China. Most parts of Northeast China are just a child, and the population reserve forces never give up, and a large number of people are lost. Northeast China should be the best place to give birth to boys and girls, and daughters are also the best place for future generations. This slogan is all over the streets and lanes, and it is also a forgotten area.