Raised christian but feeling burned out by the contradictions, the emptiness of trying to live for others (it's killing for relationships I can tell you), the mental struggle to rationalize all the rules, I too felt that spark. I realize dogmatism is always bad but that voice inside keeps saying: It's not when the theory is perfect! The truth is knowable and can be discovered through reason. How super comforting (and damn that Incompleteness Theorem I learned about later).
I don't know what it is, my hunger for a system? For rules to make sense of the world? Whatever it is, Rand's philosophy remains so appealing. It's probably the reason I started a company, walk into meetings now boldly, with a goal, why I enjoy things now, just to enjoy myself. As a rational, healthy human, there is nothing wrong with that, in contrast to what my upbringing tried to instill in me.
Perhaps that's it, it liberated my from a confining worldview. Perhaps another worldview could have done the same.