there's many ways the causality might be inversed. We tend to tell stories to justify what happened all the time, so the "strong wish" can always be a self-justification. You can also be tricked by your brain to wishing more of something by "programming" (that's positive reinforcement in practice - our brains aren't that different from other mammals). Lots of people who are successful at, say, going to the gym regularly, only do it because they found a way to create that feedback loop.

so it's likely that just "wishing something very deeply" doesn't actually lead to anything, but acting in a way that affects your mental chemistry (be it via creating feedback loops that make your brain crave more of X or simply by taking certain medicine that does it for you) does