Agreed, I think the secret is often a kind of subtlety that can often be confused with meaninglessness. For example, the first time I read "Of Mice and Men", I found the "meaningless" suffering to be infuriating - how could this book possibly be considered a classic? - until I later understood more context around the novel's time period and message, and realized it was only my juvenile tastes and expectations that made it seem meaningless (no happy ending? What is this tripe?)
I doubt Tolstoy wrote his stories without some kind of purpose, but I agree it would be a mistake to try too hard looking for meaning in case he just felt like writing up some sad shit.