Why and how did Gorbachev's reforms bring the dissolution of the Soviet Union and the collapse of its economic system?

Refer Chapter 10: The Myth and Reality of the Soviet Command Economy and Russia's Economic Transition from book Rosser,J. B., & Rosser, M. V. (2018).Comparative economics in a transforming world economy(3rd ed., Ser. 18). Cambridge (Massachusetts): The MIT Press.