For more than a century now why have so many self-proclaimed Marxist vanguard parties collapsed, self-destructed, degenerated into bizarre personality cults ?

Political science majors might select this for a Masters Degree thesis : Since the 1917 Bolshevik Revolution in Russia and those " Ten Days That Shook the World " why have so many self-described Marxist Vanguard Parties self-destructed , collapsed , or degenerated into bizarre personality cults ? Please explain . As a long time independent democratic socialist I think that a vulgar contempt for Christianity making them resonate more with the obnoxious New Atheism was a big factor in a long century of failure to reach the masses. And the biggest mistake of the Russian government -led by Lenin-Trotsky and then Stalin- after the revolution was to declare itself " officially atheist ". Also when the inner core of a Marxist " vanguard party " harbors too many decidedly neurotic Jews or crypto-Zionist Jews, with college and university educations , they invariably turn off the WORKING CLASS members. They feel as alienated in THE PARTY as they do in the capitalist factory or place of work . The political science major might focus on two parties in particular : the US based Socialist Workers Party still led by Jack Barnes and the Socialist Equality Party still led by David North. Ex-members of the SWP and SEP offer on line accounts of their experience with the " cult ".