The USSR was severely compromised. Not only did they turn on China, but the proof is literally in the fact they elected first dead end like Brezhnev, then furthermore allowed open saboteurs likes of Gorby and Yeltsin into the topmost ranks.
Actually Brezhnev wasn't that old when he came into power. And the economy kept growing in the beginning when he went into power. The problem is he stayed in power way too long, way past when he should have left. He wasn't in control of anything in his final years.
As long as USSR remains, China could not properly access the resources of the global south, and it could also not secure Russia as an ally, thereby securing energy independence. At the same time, there was no hope that the ones that allowed Gorbachev to be highly ranked would ever win the cold war.
I wouldn't agree with that since relations between the Soviet Union and China started to unfreeze even back when Brezhnev went into power. Things only started to slide backwards with China again after the Soviet intervention in Afghanistan. After the Soviets left Afghanistan then relations began to unfreeze again. For example the Su-27 sale to China was still done back in the late Soviet Union.
I think relations would have gotten better regardless of the Soviet collapse or not. But the collapse was a great opportunity for China to collect Soviet technology on the cheap for its MIC that is for sure.
USSR, unlike China, never achieved no1 economy, and never would have. Yet, they would also never have taken a junior role to China either, due to internal compromise of the CPSU, which prioritized feel good actions, leaned into oligarchy and nationalism, rather than approaching situation in the interest of all communist states.
Actually a lot of people remember about the Soviet Union poorly. The Soviet Union back in 1985 had a higher GDP in PPP than the US. It also had a higher population. Just like China does today although not to the same degree. But the Soviets had a much lower GDP/capita and GDP nominal than the US.
Sure the Soviets had a severely atrophied civilian consumer economy. But they had a huge MIC. They had a huge heavy industry to support the MIC. They were a powerhouse in terms of mineral extraction and exports with huge oil and gas sales. The thing is, after the oil price collapsed in the late 1980s, after the US and Saudi Arabia acted together to collapse the oil price, the Soviets lost most of their export income which was used by them to import technology, such as machine tools for their industry, and wheat to feed cattle. That's a big factor for why they collapsed. There are other factors. For example there was a demographic cliff when people who were born before WW2 were past 40 years old and there weren't enough young people to replace them. Which happened roughly when the Soviet Union collapsed.
Still I would say their biggest issue was they clearly showed themselves to be unable to reform themselves internally properly.
Only China, with a stable law based government coupled with the world's largest economy and industry, is able to lead the communist cause.
China also needs to continue addressing its weaknesses like high dependency on energy and food imports.
