Socialism seems to be picking up a bit of speed lately. Not Leninist Communism, which has pretty much retreated to a couple of backward redoubts - and I suspect that it's crumbling pretty fast even in Cuba and Venezuela. I'm talking instead about the kind of democratic socialism that flowered in Europe after the war.
Leninism only seems to be able to grab power by more or less violent revolution. It's big scores were Russia and China, and in each case succeeded due to the hopeless incompetence of the predecessor states. It's probably worth noting that neither of these revolutions was an utter failure. They were bloody, murderous, and ultimately economically disastrous, but they also destroyed some of the most backward elements of their local cultures. Both Russia and China remain unfree autocratic states, as they were before their revolutions, but neither is still Communist or even socialist. That happened because their leaders realized that the Communist systems were not economically competitive. There is some hope that Cuba will realize the same thing, if the right-wing Cuban nutjobs can be persuaded to let it. Venezuelan semi-leninist socialism seems likely to collapse under the weight of its own incompetence and corruption.
Democratic socialism wasn't a success either, and all the democratic socialists societies have pulled back many of their socialist experiments. Again, its central failure is inability to compete. The more extreme versions of socialism, at least, cripple the entrepreneurial spirit that yields innovation and economic growth.
So why does this hardy perennial, or weed, if you prefer, keep coming back? Those who know more economic history than I say that it's because Marx's critique of capitalism had many valid points. In fact, the most successful capitalist societies of today have adopted many socialist ideas - social security, national healthcare, public education.
Despite the constant whining sound from the right, these hybrid societies show little sign of turning into Communist hell holes. On the contrary, the extreme inequality produced by untrammeled capitalism breeds fascism and its reaction.