Why did the Communist regimes collapse in the Soviet Union and eastern Europe, but not in China?

Nobody can say definitively the reason(s) why the communist regime that has ruled China since 1949 survived, while those regimes that governed the Soviet Union and its East European satellites collapsed. One major reason, however, is almost certainly the fact of China’s adoption of capitalist economic practices following the death of long-time communist leader Mao Tse Tung. Mao was a strict doctrinaire adherent of Marxist-Leninist principles and was responsible for tens of millions of deaths among the Chinese population as a direct result of his economic policies. Following his death, and the spectacle of the so-called “Gang of Four,” newly-ascendant Communist Party leader Deng Xiaoping set out to fundamentally reform China’s economic system. To the surprise of millions around the world, Deng’s changes included the introduction of capitalist practices that resulted in phenomenal levels of economic growth. While China’s middle and upper classes grew rapidly (in fact, China’s middle class is today larger than the size of the entire US population), the Communist Party did not relinquish any control over the country’s political system. The harsh autocratic governing structure founded by Mao and his colleagues and followers remained in place, most famously evident in the brutal crushing of the Tiananmen Square uprising of 1989.
China’s experience contrasts markedly with that of the Soviet Union and its satellite regimes in Eastern Europe. With the rise of Mikhail Gorbachev as leader of the Communist Party of the Soviet Union in the mid-1990s, fundamental economic change was accompanied by political transformations that seriously weakened the governing structure. Gorbachev’s policies of perestroika and glasnost (reform and openness) represented a far more dramatic shift away from dictatorial government than anything the Chinese have implemented. In fact, the Chinese Communist Party views the Soviet Union’s experience as a model to be avoided at all costs. This is the main reason China has not gone down the same road as the former Soviet Union. Both systems failed. The Chinese, however, adapted without relinquishing power.
http://www.chinadaily.com.cn/opinion/2007-10/19/content_6243676.htm

https://thediplomat.com/2018/06/chinas-reform-and-opening-40-years-and-counting/

https://www.bbc.com/news/world-europe-31733045