How I interpret this it that working hard increases your skills. If you are more skillful you are more able to take advantage of lucky situations you have. We all have lucky situations, some more than others (we can even say privilege plays a large role here). But here's the thing, if you don't have the skills to take advantage of these situations then they are useless.
Let's make up an egregious example. Let's say you are working on battery powered rockets that use AI. If you one day meet Elon Musk at your local grocery store and somehow strike up a conversation then he's probably going to be very interested in you and your background. He'll probably try to keep in contact with you and maybe offer you a job. Now let's consider without the skill. Well you met Elon Musk which is pretty cool, but you're probably not going to get a job.
It isn't so much luck vs skill, but the combination of the two. I would be willing to bet that there is not a single millionaire (yes, that low) that can't chalk up a significant portion of their wealth to something that others would consider luck. Such as family/friend's connections, stumbling into a situation, taking jobs that lead to other jobs in the right way, etc (this is why the specific wording of the previous sentence. Because most don't notice these kinds of things and when looking from the inside we notice the skill part and not the luck. Because we did in fact work hard, and you know... Human psychology)