"Whatever doesn't kill you only makes you stronger" [Gone Religious]

I was listening to this podcast on my walk today morning and it had a bit about how Manichaeism influenced Augustine. 

He became a believer in Manicheism. Manicheism was a Gnostic religion back then that was actually a pretty serious rival to Christianity during the times of Saint Augustine. Basically, the idea behind it was that, I mean, God wasn’t all-powerful, and that in actuality all the things in the world are controlled by a dualistic cosmos. I mean, in the case of Manicheism, there were two forces, good and evil, constantly battling against each other. And it should be known that these two forces in themselves are actually extremely complex, and they represent a lot of different things. Many times, the Good represented the higher spiritual existence, and Evil represented the material, flawed lower existence. Huge fans of philosophy might consider it similar to Empedocles’ view of the forces of Love and Strife. [Transcripts quoted verbatim]

Further, a few seconds later, he said

But really, one of the great things about Christianity is that it kind of has everything. I mean, there are Christians today who believe in something very similar to that. They believe that the devil exists and has the power to intervene and try to influence humans to do his bidding. You know, the devil tries to get us to do bad stuff, and God tries to give us strength so that we won’t succumb to his temptations. The similarities to Manicheism are obvious.

I found this to be very interesting. Christianity and Manicheism were both competing religions in the 3rd Century CE. One survived, the other didn't. What's interesting is, the one that didn't survive was essentially absorbed into the one that did.

Is this true for other religions too?

I think it could be true. After all, all religions in a way offer answers to our existential questions. People, I've noticed, ask questions not because they want answers, but because they want someone to tell them that the answer they already have is true. People want support for their worldview. As long as there's different kind of people on this earth, different religions that offer different kinds of answers will always find takes. A religion that is vague enough to seemingly offer different sorts of answers to the same question would have higher survivability than its competitor.
In the 3rd Century CE, when Manicheism and Christianity were competing, neither answered all the questions to everyone's satisfaction. Somehow, through brute strength, historical luck or some clever persuasion, Christianity found itself to have a slight edge. Eventually, as Manicheism started receding ground, Christianity maintained and improved upon this lead, not by staying the same, but by absorbing the good (meaning effective) ideas from Manicheism.

This kind of interplay must've happened elsewhere too. I'm not sure right now, and this needs more reading, but I'm sure a part of the reason Hinduism survived for however long it did because it's vague in places it cannot afford to have a narrow span of available answers to life's questions.