This article makes a succinct argument, but essentially the reasons for its fall:
- The cold war arms race upped by Reagan - a huge drain on both material and mental resources that would've been better allocated to other industries. The US's constant military pressure and brinksmanship forced the USSR to play catchup against an opponent with a larger chip stack.
- The USSR acted as anchor and banker to many third world revolutionary projects, which proved an additional drain on its economy. PRC avoided this mistake by being strictly non-interventionist, and avoiding these dangerous foreign policy traps.
- De-linking from the world economy and not being able to take advantage of the newest technology and consumer products from the west. The PRC corrected this mistake by the 1980s.
- Capitulations by Gorbachev to begin the process of privatization and dismantle the planned economy. PRC also avoided this by strengthening its publicly owned portion of the economy, refusing to privatize them, and making sure they commanded the top position.