No, I'm not saying that it is unknown, but that some people like to claim that Paul created Christianity despite evidence that there were groups of what we now call 'Christians' before he arrived on the scene.
Christian is only Greek for Messianic. But there were other Messiahs, who had their own cults, which were also called Christians.
Those other Christians didn't disappear - they fused. Which is why Irenaeus had to treat their leaders as Christian heretics. Simon Magus thought he was the Messiah himself, and his views were still current within what Irenaeus regarded as the Church. That Church certainly wasn't Orthodox.
Nowadays Christians like to have it both ways. They'll claim for Jesus early cults and movements about whose beliefs we know nothing. Then the next minute, any modern movement that's slightly off-line will be deemed not Christian.
As for Paul, he started Jesus cults in small places, but every major city he visited, even Damascus, had a small Jesus cult already. I don't think he or his views were widely known until his letters were circulated.
But the massive contribution of his letters was the whole theory that salvation was possible because of the sacrifice of Jesus.