What role does pure luck, or chance, have in academic careers?
A lot of things that seem to be luck are really not, since fortune favors the prepared mind, as Louis Pasteur supposedly said. In other words, you can put yourself in the position to make a lucky discovery. You submit enough good articles to good journals and you get some acceptances. What you are really doing is stacking the odds in your favor.
On the other hand, things that seem to be undetermined by chance actually are sheer accidents. They offer a job to one person, who turns it down, and you get it instead. You happen to go into a field that later turns out to be hot and offers you more possibilities.