Huh...she didn't...
Did you even read the article?
Here it again:
The Progressive worldview, and the Libertarian, Rand-worshipping worldview -- are all part of the same existentialist family tree containing Sartre and Alinsky. Rand's humanistic objectivism is as cold and Godless as Sartre's humanistic existentialism. These pseudo-intellectuals are the reason Christianity has been quietly erased line by line, year after year in the popular psyche.
She is not making a comparison, just they have the same result..."Christianity has been quietly erased line by line, year after year in the popular psyche"
Really, it's not that hard to understand...
The strongest and most effective part of Ayn Rand’s writing is against collectivism, not against Christianity. That’s why leftists universally hate her while a sizable minority of conservatives like her. It’s not just Christianity that’s in retreat nowadays, it’s the general principle of individual liberty, which most conservatives consider foundational. Rand wrote powerfully in support of the general principle even if she didn’t get there via Christianity.