Well that's predestination, he was the Sisko because he's a half prophet. What's so particularly special about him otherwise?
Nothing. That's the point - he's not half prophet (although he did ascend that wasn't presented as being unique to him), but he always had been, always would be the Sisko. Sarah was possessed by the Prophet to create Sisko because there had to be a Sisko because they meet him when he comes into the wormhole in his future (but their present).