In my most recent job hunt, I interviewed three times. In the first two loops I tried my best, but I could feel I wasn't really connecting. In my third, they asked questions about the kind of thing I had just spent six years building and I connected perfectly. It was like the sensation of hitting a homerun in the third loop, compared to foul balls (or strikes) in the first two.

In a way, this is luck. How lucky for me that the third job fit what I knew about and was comfortable talking about. It was lucky that they asked the kinds of questions that were things I was very experienced in. I was the same candidate in all three interview loops, just unlucky in the first two that what they were looking for wasn't a good fit for what I knew, and lucky in the third that it was a good fit.

That said, there's also a way in which this isn't luck. That is, I had to have some area of knowledge and skill or else I would have been flailing around forever without connecting.

Any individual interview is luck, but hard work and experience can increase the size of the target you're hoping to hit.