Why has class conflict not occurred in the form expected by Marxist analysts and why has history not developed in the way Marx predicted?

Karl Marx (1818  83) was responsible for one of the first and most influential theories of class within the sociological discipline. For Marx, classes can be seen as basic social groups divided by their specific position within the division of labour, and distributed within society according to criteria such as ownership or non-ownership of the means of production and the need to sell or ability to buy labour. Marx also distinguished between a number of modes of production that were used to chart the sequence of historical development that resulted from changes in the economic base of society….(short extract)