Ironically the opposite also can happen. I became an atheist by buckling down and reading the bible to shore up my faith to prepare for a morality disagreement with my parents...
Only made it to god giving permissions to have slaves in exodus when I stopped and asked myself... wait I'm looking to this guy for my ideal morals?
People who read communist theory become communists for the same reason that people who read the bible critically become atheists.
Yup... bottom line reading something critically, expecting it to be what everyone told you it was... and paying attention to discover it as the opposite.
In some cases something you thought was profound, turns out to be bullshit, fluff or just horrific.
Or in other cases something you thought was nonsense... turns out to be right about everything, down to it's predictions of the horrible directions capitalism/imperealism would lead to, looking around and going, shit he predicted it almost perfectly.