In what way were Karl Marx's views different from the socialism advocated by Owens and Fourier?

One key difference between utopian socialists (Owen and Fourier socialism) and other socialists (Marxism) is that utopian socialists generally do not believe any form of class struggle or political revolution is necessary for socialism to emerge. Utopians believe that people of all classes can voluntarily adopt their plan for society if it is presented convincingly.