I recently asked the question What is C. S. Lewis' opinion about homosexuality?. The question was closed as being off-topic.
Are questions about authors' personal opinions on-topic or off-topic?
I wrote about this issue way back on Area 51, and much of the below is copied from my answer there.
Learning about authors helps us to appreciate their works better. If we want to learn more about works of literature (or any art, really), part of that involves looking at the people who created them. Why did they write it like this instead of like that - what inspired them to do so?
Knowing these details about the author's lives helps us to analyse their works.
An important question in any discussion where we might end up ruling one class of questions on-topic and another, but very similar and closely related, class off-topic is: where do we draw the line?
Let's look at some example questions, partly drawn from Area 51 (some of which have by now been re-asked on the site) and partly from actual questions on the site:
How has experience in WWI influenced Tolkien's writing?
This is actually more about Tolkien's books than about the man himself. The question is deliberately phrased in terms of the influence on his works, which should place it very firmly on-topic despite involving details of his life outside of writing.
When and why did the Brothers Grimm start collecting fairy tales?
The highest-voted question from the definition stage, this could be seen as more about the authors than their works. OK, it's about how their magnum opus came to be, but any answer would likely be about their real lives and not about literature per se. This question has been asked on the site, and is currently very highly-voted with no pending votes to close.
Where did Margery Allingham talk about "polishing her prose until it shone overbright"?
This again seems to be more about an author than her works as such. It's been asked on the site, and currently has a positive score with no pending votes to close.
How much experience did Tolkien have in writing?
This question is definitely more about the author than about his works, although it's definitely also relevant to his works and appreciation thereof.
How did the Inklings originate?
This question (self-promotion alert!) is entirely about real-world authors and not at all about their works as such, but (as I mentioned in a footnote on the question itself) I believe that knowing more about the real-world origins of the writing group might help us to appreciate the literary works which were shaped partly through meetings of that group.
All of these examples, except the first, have now been asked on the site, and all have been well-received: currently with positive scores and no pending votes to close. It seems that community opinion is in favour of questions about authors, at least provided they make some effort to justify a connection with works of literature. Your example doesn't, which may go some way towards explaining why it was so poorly received and quickly closed by three normal users and a moderator.
Back on Area 51, I said that "questions about authors are more likely to be on-topic if phrased in terms of their works", and used the first of the examples considered above to illustrate this point: "Where exactly did Tolkien serve in WWI?" might or might not be considered on-topic, but "How did his WWI experience influence Tolkien's writing?" would surely be fine. Now I would probably rephrase my statement in terms of quality rather than scope, and recommend downvoting rather than voting to close for questions about authors which aren't sufficiently clear in explaining a connection with works of literature. However, I'm open to being persuaded on this point - I realise we don't want the site to get overrun with random biographical questions about every author ever (did Tolkien drive, what's George RR Martin's favourite sandwich, how did JK Rowling do in maths at school, etc.), so if we start seeing too many of these, then maybe close-voting will have to be the way to go after all.
By the meta discussion, if you're asking whether they wrote about it and what they wrote, it's on-topic.
Are questions about authors on-topic, or just their works? For example, asking about authors lives, motivations, interviews, or anything relating to their work.
I would say that they would be on-topic, but only insofar as they relate to an author's literary life.
We had a similar issue on History of Science and Mathematics early on. Would a question about Einstein's favorite style of eggs be on-topic? Obviously not, because, as far as we know, eggs did not have any role in Einstein's scientific work. Extrapolating that here, I don't think that a question about J. R. R. Tolkien's favorite sandwich should be on-topic, but I do think that a question about whether certain portions of his books related to certain events in his life should be on-topic.