Analyze the economic, political, and social causes of the Soviet Union's collapse from 1985 to 1991. Evaluate how Gorbachev’s reforms (perestroika, glasnost), systemic economic weaknesses (central planning failures, declining oil revenues), political shifts (elite divisions, the 1991 coup attempt), and rising nationalist movements within the republics interacted to produce disintegration; use evidence to weigh the relative importance of these factors and identify key turning points.