It's up to the answerer if they want to match the answer to the asker's level, or to also extend their answer to a broader audience.
In general, the purpose of Stack Exchange is to create a library of good and high-quality Q&A for everyone; not only for the asker but also for future readers.
That's also the reason why SE allows multiple answers on the same question. For technical questions, there are possibly many ways to solve an issue. But for more theoretical questions (like on this site), multiple answers are generally encouraged as long as they are not a duplicate of another answer and also adding new insights (significantly) to the existing answers (either by extending or contrasting them).
Then in an ideal situation, the voting will indicate which answer is the most helpful/useful according to the community or public (contrasting the accepted answer for the asker only).
It's actually possible to cater an answer to a broad audience by using general-to-specific/deduction approach: composing an answer starting from a general/broader topic (i.e. the overview), and then moving on to the specific topics (i.e. the details). With this approach, newcomers can follow the answer starting from the basic, while more advanced readers can skip the basic but still getting new insights from the detail on the topic. Of course, there's still a balance between the length (up to 30000 characters)/detail where the answerer needs to know when to stop...