Yeah, that seems to be the crux of the matter: once people realize that the main religions are frauds, they are tempted into the toxic materialistic belief system which leads to nihilism. And vice-versa - once they realize that materialism and dogmatic scientism is nonsense and soul-destroying, they go right back to the main religions, which are frauds...
I beg to differ. The people I know may not be a cross section of the general population, but my personal experience is that those who are disappointed with a certain religion are rather moving either to another religion or some esoteric or "new age" movement. If they'd rather turn materialistic, chances are that they will have been all the while.
I have yet to meet a materialist or a dogmatic scientist who realizes that materialism is nonsense, let alone soul-destroying. That would probably be asking too much of them.
When dissatisfied, they would rather look for a new and improved materialism including state-of-the-art paraphernalia.
But I would be hesitant to declare that all materialists are prone to nihilism.
Experiencing a major jolt in life, though, could actually have materialists look for a deeper meaning in life...