It's not literally impossible to win the lottery cos as you noted, people do win. The chances are extremely low though; they've done the math of 1-in-chance for the various lotteries depending on the format of the game.
edit: Looked it up, Powerball is 1 in 175,223,510. /calculated
Wrong question here. Or rather, not enough possible answers given as possibilities. You're not considering every option. Everything is causal determinism. Calling it any of those other things - luck, karma, etc. - is just a placeholder word that confuses the reality of the situation. It's saying "I'm not sure how everything happened, so I'm going to give it a word that's ambiguous enough to encompass that confusion."
Some definitions of karma that I've seen are basically synonymous with determinism, and some definitions of luck can be incorporated into a deterministic worldview. But then it begs the question of their use at all, when they are used to mean so many other things by people.
If you drop an apple it falls. Ergo, the universe.