The Soviet state was centrally controlled and Gorbachev had enormous power as General Secretary of the CPSU.  I recall an interview with Gorby where he described a talk he had had with Shevardnadze once in Yalta.  They were both extremely frustrated by the constraints of their system, paradoxically.  They expressed that frustration as "We cannot go on living like this."  

Gorbachev's reforms aroused fierce opposition amongst many in the nomenclatura who rightly feared that these reforms would be their own undoing.  The Soviet system never considered that the whole system could be taken down by a determined General Secretary.  Gorbachev used events to put allies into key positions.  My sense has  been that, while he wanted to steer a more moderate course, in the face of resistance from hard-liners, Gorbachev essentially ended up using the political power he had as General Secretary to bulldog the existing system  by pushing through a new Constitution, holding elections, breaking the political monopoly of the Communist Party, breaking up state enterprises into smaller private enterprises and shedding the buffer states.  

I suspect that he thought he could more successfully influence the future direction of the Russian state and society and its relations with the former buffer states than in fact proved possible.  Less drastic reform efforts may well have failed and left the old system largely intact.  I consider Gorbachev to be a great historical figure.  We need a similar determined reformer in the USA.  May we be so fortunate as to have one.

"It is not necessary to have hope in order to persevere."