Gorbachev's assumptions in 1985, when he set out to revitalise the Soviet system, were clearly very different from those he held by the end of 1990, when everything was falling apart and state socialism had been rejected across Eastern Europe. And when he looked back later, he sometimes tried to rationalise what had happened in a rather self-serving way. The man was a politician, after all, and few politicians are prepared to admit, even to themselves, that their policies turned out to be disastrous.
But the main problem with the 'Gorbachev was a traitor' arguments is that they are so boring. It's all simple - no need to look critically or analytically at the USSR, its society, economy, politics, development, and problems. No need to try to understand anything at all. No need to engage the brain. It's all the fault of the bad man and his bad intentions. There have been innumerable fascinating and insightful discussions about Soviet history, from start to finish. There have been hundreds of excellent books and articles (as well as thousands of dire ones). But these discussions have, for the most part, been taking place outside of the structures of what remains of the communist movement. That is unfortunate, but scarcely accidental.