It sounds strange but it makes sense once you understand how Google thinks. When a website spends years writing deeply about one subject, Google begins to see it as a go-to source for that topic. At that point, Google starts matching the site to many different searches related to that subject, even searches the site never planned for. It is called topical authority, and it basically means the site earned Google's trust over time. The traffic is not accidental, it is just the result of covering a subject well and consistently. Do you think most content creators focus too much on chasing individual keywords instead of building that kind of depth?