What causes socialism?

Answer 1

Socialism is a product of a long line of philosophy originating in Europe beginning during the Enlightenment. Much of this thought developed in France, although theories were also put forth in Germany, Italy, and Great Britain, among others.

It served as a basis for the theories of Karl Marx and various elements are present in most countries to some degree. Most significantly in northern and western European countries and communist states.

If you are referring to a more specific answer as to why a state might become socialist, the number of factors expands widely. These include education level, poverty, population size, GDP, and general historical factors. There are of course many more variables though.