" ... issues of right and wrong and how the past impacts on the present.
"Crime fiction is always about the past: it begins with a dead body and the detective has to go back to work out what happened. The whole genre is about starting at a point in time and then tracing back to work out where it all went wrong."
This explains why crime fiction, like historical fiction a genre with a vast variety of sub-genres, including crime investigators from all eras, appeals to so many historians. I had noticed quite some ago that crime fiction is sort of universal genre solvent -- it dissolves successfully into every other form of fiction there is, and this must be why.
Thank you Mr. McGillowy!