Why has China become superpower when the Soviet Union collapsed? I think two reasons. One China made up with America after the death of Mao. They made diplomatic and economic relations with America. Two China allows private sector. Much of the Chinese economy is private enterprise owned by private individuals or by international corporations. So it has grown greatly while Soviet economy failed. Maybe the Chinese are smarter than Russians? They saw communism doesn’t work and made needed reforms
The Soviet Union's collapse has nothing to do with China's rise.
The USSR was never an economic superpower - only a military superpower - mostly due to its' nukes. Communism doesn't work - so the USSR economy was destined to fail.
China?
Simple mathematics - what happens if capitalism is introduced towards a market/country with 1.4 Billion people - who are known to be thrifty businessmen since 2000 years? This happened in 1980 approximately 10 years before the USSR collapsed. - a Monetary Explosion of unprecedented volume. In other words, what took the USA or e.g. Germany a 150 years, took China less then 40 years.
Till today China is nowhere near the per/capita income of e.g. USA or Germany. So calculate their GDP onto an equivalent per/capita based on 1.4 billion people. Theoretically an unstoppable never before in human history ever existing economic Super, Super Power, in likely 25 to 30 years.
Foreign investment and technology transfer:
Initially (first 10 years) almost solely conducted by Oversea Chinese - and Chinese from Taiwan. From 1988 till 1995 Japanese investment and technology transfer came in. By 1995 the EU and the
USA started to recognize the now already available economic platform that Deng Xiaoping had created from 1980 onward.
The USA and e.g. Germany had castrated their own economic cycle via constantly increasing company profits and it's owners and management getting richer and richer, and prices for goods constantly increasing, whilst ignoring or rather suppressing the income cycle of it's workers and employees. Logically if the workers and employees don't get enough $ they can't participate accordingly in the increase of consumer spending. The Western political action was very simple and unified - let's take up debts in order to artificially increase consumer spending aka increase the GDP growth artificially.
Cooperate greed and political incompetence in Western countries - did not lead towards an increase of peoples income, thus not allowing for goods Made in USA or Made in Germany to be increased or at least to be held on the production basis/ratio of 1990. Instead Western-Importers from 1990 onward realized their own economic super chances - thus enhancing China's industry output and workforce hugely.
From 1980 - 2000 the EU countries and the USA population started to appreciate "cheap goods" from China but mostly stayed within their personal financial frame, Very unlike the USA where consumer spending was getting more and more out of hand to factual income - but personal debt making became absolute fashionable - the American way of life.
Therefore from 1995 onward, US and EU based manufacturers lost out to competition from China increasingly. Instead of raising incomes and invest into their own countries - everyone started to run to China - totally brainless and ignorant towards the Asian and Chinese business mindset (the vast majority of US and EU companies in China never made profit until today). Only those US and EU companies directing their investment towards the China market made it and are still around. Those having invested to compensate/divert their own home production and demand - booom, and in vast majority having been taken over by Chinese investors - thus again adding hugely to technology transfer.
Back to Russia: No overseas Russians were willing to invest into a total chaotic new Russia. Controlled by non state and state run Mafia organizations and becoming the present day Oligarchs.
US and EU investment only really started to come in from 2000 onward, due to to a strong hand ruling Russia - Putin. At the same time Western investment in Russia was in contradiction to the EU and foremost NATO policy towards expansion (the latter two aiming at controlling, partially destabilizing Russia's economic influence - as such it's growth). According to the US and EU logic - more $ for Russia might result in Russia spending more $ towards it's military.
China never had such intentions towards Russia and was therefore able to drastically improve it's political and economic relationship with Russia. Putin was initially no big friend of China, he was actually quite "pissed off" at e.g. China's attempts towards technology transfer in regards to military matters and it's considerable economic influence in the Russia/China border areas.
However thanks to NATO's "games" in regards to Georgia, Moldavia, Ukraine and some other Russia neighboring countries - he found it best for Russia to align with China and work out issues in a way, so that both sides profit from each other - most warmly welcomed by China. E.g. okay we buy Chinese products - you guys buy more natural resources - instituted way before the Ukraine crisis.