Stalin died less than a decade after the soviets' incredible victory against the nazis, which made him loved by a ton of people. And then the party decided to undo everything he did? You could debate whether stalin was good or bad, but my question is what made the party switch directions after stalin died?
I'm no defender of Khrushchev, but he did not push for the restoration of capitalism (not that the USSR was doing socialism to begin with) at all, that's some ridiculous revision.
For why destalinization happened, the party was incredibly traumatized by the purges combined of course with some personal opportunism, and legitimate belief that changes needed to be made for the ussr to move towards communism.