Well, Marx said that capitalism was needed to bring about a highly industrialized nation, which would be made up of a large working class population. He believed that it would be a natural process for this working class population to gain a class consciousness and therefore overthrow the oppressive capitalist regime. So barring propaganda, a nation would proceed into socialism after it becomes highly industrialized. Obviously, nation like Russia and China jumped the gun there, which is partly why they were not able to institute a true socialist society. And many European Nations and the USA have used propaganda in such an effective manner as to convince the people that socialism is bad. Additionally, those nations have done a great job infiltrating trade unions and such to quell the development of class consciousness.
The reasons behind their ultimate destruction lie in many places - dogmatism (I'd definitely say is one), invasions from capitalist nations (e.g. Bay of Pigs, Russia got invaded, too), isolation - via trade, transport, etc, and the material conditions surrounding these revolutions.
Indeed, look at Russia's economic state before the revolution! For anything to succeed there without many hiccups and problems would have to be a fucking miracle!
You need to understand that there are two types of Communism. Libertarian Communistm and Authorotarian communism.
As a Libertarian communist, I would argue the model for revolution utalised by communists over the last 90 years, or more specifically the existance of a vanguard party as a key feature of that model, is inherantly flawed.
Communist revolutions have failed to destroy capitalism due to inherant ideological and practical flaws within Authorotarian communism.
The failures of authorotarian communist revolutions were actually prediced decades before the Russian revolution when Communist/Anarchist thinker Bakunin said "Even if you took the most ardent revolutionary, vested him in absolute power. Within a year he would be as murderous as the Tzar himself" - this statement has of course been absolved.
And if humans inherantly want stuff, and capitalism is a system that sees the concerntration of wealth in fewer and fewer hands, surely capitalism is against human nature?
Tons of corn is dumped in the sea every year to make remaining stocks more valuable. Food is deliebratly underproduced for the same reason. Whilst millions starve. That doesn't sound very efficient to me.
This isn't what I think. It is what marxist think but they do make good points