How did the Revisionists overthrow Socialism?

Khrushchev overthrew socialism in USSR, Deng Xiaoping overthrew socialism in China, Ali overthrew Socialism in Albania.
How is it that these revisionists managed to come into power and restore capitalism?

Well personally I don't think any of those forms of socialism were done right but what it comes down to a lot is the people as a whole feeling as if they are being oppressed, which is exacerbated by foreign support, and eventually change occurs either peacefully or violently.

In terms of people just deciding to do reforms, overtime some people may have thought it'd be better for their country to integrate into capitalism to improve international relations, trade, etc.

We can only really speculate, have no idea what these people thought when they did what they done. Could've been their belief it'd be better for the country, maybe personal gain, or something in between.

I believe David Kotz provides the most persuasive explanation in Revolution From Above: The Demise of the Soviet System, i.e., that the problem was with centralized economic planning per se. Simply put, the nomenklatura of the state socialist regimes constituted something of a non-capitalist quasi-class whose position vis-à-vis the means of production was such that privatization was an attractive measure to undertake because they stood to personally benefit from it. The revolutionaries in Russia, China, Cuba, Yugoslavia and so forth could be entrusted to abstain from behaving in an analogous manner because they were principled communists. Once said revolutionaries passed away, however, various bureaucratic careerists, with no particular attachment to either Marxist theory or socialist political philosophy, inherited their positions of power and the inevitable result was capitalist restoration.

The obvious implication of this is, unless the means of production, distribution, and exchange are genuinely socially owned and democratically managed, a socialist mode of production cannot be sustained.

Celtiberian wrote:
The obvious implication of this is, unless the means of production, distribution, and exchange are genuinely socially owned and democratically managed, a socialist mode of production cannot be sustained.

This is the contention of S.G. Hobson, made with enormous foresight, and I'm entirely convinced by it. He argues for the socialist state, however it manifests itself, to be accountable to democratic monopolies of labour (termed National Guilds).

Is this the same, or a similar, contention of syndicalism? I'm admitting my ignorance, but I've encountered syndicalists who fully accepted Guild Socialism (as just another term for their own system) but others who were totally against it (as just another term for fascism or social democracy).

Scarlet-Left wrote:This is the contention of S.G. Hobson, made with enormous foresight, and I'm entirely convinced by it. He argues for the socialist state, however it manifests itself, to be accountable to democratic monopolies of labour (termed National Guilds).

Is this the same, or a similar, contention of syndicalism? I'm admitting my ignorance, but I've encountered syndicalists who fully accepted Guild Socialism (as just another term for their own system) but others who were totally against it (as just another term for fascism or social democracy).

It depends entirely on which model of guild socialism you're referring to. G. D. H. Cole's conception is certainly analogous to what revolutionary syndicalists advocate(d)—i.e., a mode of production wherein productive and distributive assets are publicly owned and democratically managed by the working class—but the same cannot be said of, say, Arthur Penty's proposals.

Having said that, where syndicalists and guild socialists possess an irreconcilable difference of opinion is on the subject of tactics. Syndicalists are revolutionaries who believe socialism can only be achieved via direct action undertaken by the proletariat, while guild socialists (at least historically) are piecemeal reformists.