Soviet Communism survived, it did not survive unchanged.
> it became more stable as Stalin was driver of instability at the top.
Asimov would, based on the fairly explicit statements in the review on the topic, say that it got more stable precisely because it became less totalitarian.
I’m not interested in arguing whether Asimov is right on this point, but it is indefensible to claim that his painting of Stalinism as tyranny that was explicitly repudiated as such by later Soviet Communism is an apologia for Stalinism.
"Let them cope by themselves. I've done the main thing. Could anyone have dreamed of telling Stalin that he didn't suit us anymore and suggesting he retire? Not even a wet spot would have remained where we had been standing. Now everything is different. The fear is gone, and we can talk as equals. That's my contribution. I won't put up a fight."
That is not what instability of regime means. It does not refer to individual being forced to retire. The regime itself was more stable then before. Khruschev retirement did not weakened nor endangered regime.
Stalin did changed people on top too. Some changes and power struggles after his death are not more instability or "touched" communism.
Khruschev was the first one retired. Powerful people before him left power dead (by execution) or by being imprisoned forever. That is being more stable.
It did became safer to both hold power and not to hold it in Russia after Stalin death.
Instability compared to what Asimov sees as Orwell's perspective that Stalinism is impervious to internal erosion (including death of the leader.)