luck is a default explanation. it's what we say when we don't know. It's an attribute to a mystical force for which there is no tangle proof. Is an unlikely outcome due to voodoo or witchcraft? Most people would say no. But we talk about luck all the time when it's the same explanation.
When we analyze or explain outcomes in sports we are dealing with complex systems, so we invent things that help us (models, descriptive and inferential statistics, spray charts, etc.). Those inventions are often useful, but never perfect.
I saw a post saying the Brewers got lucky this year because they didn't have a guy have a huge year. When in fact, the brewers are the organization that the Cubs aspire to be. They know how to pick players that fit their model and plug them in to get the best outcomes. It's not luck that they continue to dominate our division.